Congratulations! You've signed up for Microsoft's Windows Insider program, downloaded the Windows 10 Technical Preview ISO file, and are just about ready to install it. Consider this your orientation for your new operating system.
Brad Chacos has already outlined the steps for downloading and installing the Windows 10 Technical Preview on a virtual machine or hard drive partition. I went the simpler route: I took an older machine (a Surface 2 Pro), wiped it clean, then reinstalled and updated Windows 8 to the present.
Windows 10 installation: the final steps
If you have a spare machine lying around, updating to Windows 10 is extremely simple, especially if you have a spare 8GB USB key at the ready. As Brad recommends, back up all of your spare files (photos, documents, saved games, etc.), preferably to an external hard drive or OneDrive, just to be safe. Then jump into your Start screen and type "create a recovery drive." Click on the search result. In just a few steps, Windows will copy your PC's recovery drive to the USB key, erasing whatever was stored on the USB drive in the process. This is important, as after you upgrade to Windows 10 there's no going back.
After you've created your recovery key, make sure that the Windows 10 ISO file is copied to an external USB drive, DVD, or flash drive. From there, swipe right to access the Charms, select Settings, then Change PC Settings. Click on Update and Recovery, then Recovery. Clicking the "Restart Now" button under Advanced Startup will reboot your PC, and allow you to select the media on which you've stored the Windows 10 Technical Preview ISO file.
From there, installing the ISO should be relatively straightforward. Your PC may have to reboot several times over the next 10 minutes, but it can be left unattended. You'll know it's completed when your PC begins a Windows 8-style setup process: You'll be asked for your Microsoft account; whether you want to sync your settings with another Windows machine; whether you agree to some legalese; and to input a verification code that Microsoft will email you. After that, Windows 10 will load your applications, ask you for your username and password, and dump you unceremoniously into the Windows 10 desktop. You're done!
A couple of caveats before we continue: This build of Windows 10 will run on multiple monitors, but some of the snap features work best on a single monitor. And make sure you have a mouse--Windows 10 isn't especially touch-friendly at the present. I never had any problems inserting a mouse, but plugging in headphones generated an error message.
Welcome to Windows 10
I'm not going to lie: Your first moments with Windows 10 are going to feel somewhat anticlimactic. If you've synced your settings with another machine, you'll see the same desktop background as before. But wait, that toolbar looks different--there's a search icon, and a weird icon to the right of that: It's the task view, as you'll find out later.
Ah! There's the Start button! Click it and you see...the Windows 8 Start page?!
Yes, you do. And that's the last time you'll ever see it, if you so choose. Right-click the toolbar, select Properties, click the Start Menu tab, and click "Use the Start Menu instead of the Start screen." Sayonara, Start Page. There's only one odd caveat: Opting out of the Start screen for the Start menu requires you to log out and in again. I have no idea why.
Now click the Start button one more time to bring up the Start menu. Yes, this is why you downloaded Windows 10, isn't it?
How to tweak your Windows 10 Start Menu
With a little tweaking, the Start menu can be a powerful tool. Note that it, too, is a window. By hovering the mouse over the edges of the window, it can be dynamically resized. But leave it as it is for the moment.
On the left, the Start menu provides a list of applications and locations that you'll access frequently: Documents, Pictures, PC Settings, and the File Explorer tool are all at the top right. If you go back into the toolbar settings menu, you can also click a series of checkboxes to specify which folders and locations are shown in the upper list. At the bottom of the menu are two important buttons: "All Apps" and a Search bar. We'll come to back to Search later.
Clicking "All Apps" lists all of your apps, in alphabetical order. But it's also a gateway to the Live Tiles to the right.
Now why are those Live Tiles there? Well, they can be shortcuts to frequently accessed apps, certainly. But they're also live widgets that can dynamically update you on your mailbox, the weather, sports news, and more. You'll see some Live Tiles already populated; feel free to right-click each and resize them, for example, or move them around. If you want to add more Live Tiles, open the "All Apps" list and drag one of the apps into the Live Tile region, then right-click it and turn the Live Tile capability either on or off. You can also tell the Live Tiles not to display personal information, via the Start menu preferences.
Finally, you can resize the Start menu, transforming it from a skinny skyscraper to a massive window that evokes the Start page. Adding Live Tiles at the edge can increase its size. You can also click and drag the top edge down. Use a mouse, though--this early build isn't overly touch-friendly.
Making the most of search in Windows 10
Search worked fairly well on Windows 8. On Windows 10, entering a search term in the field suggests either a file on the local machine, a webpage, an app on the Windows Store, or a portal to the Bing underworld, where an HTML page opens up displaying results for, say, Fleetwood Mac. Clicking any search result then launches Internet Explorer.
There's not much to tweak here, but some of the more innovative features--such as launching Xbox Music when a song is searched for, or rendering "hero pages" when searching for celebrities--aren't connected yet. (Xbox Music does work, however.) With Windows 8, Microsoft attempted to remove search from the browser. With Windows 10, it's just doing a better job of it.
How to snap apps to the four corners of Windows 10
As noted previously, you can run Windows 10 on multiple monitors; I hooked an external monitor up to my Surface. But one of the features that Windows 10 offers--four-corner snap--works best on a single screen.
It's really quite simple: Drag a window to a corner of the screen, and it will snap to one-quarter of the display. Snap it to the right or left, and it will cover half the screen. Just like the Charms bar is somewhat problematic on multiple monitors, however, so too is four-corner snap on an extended display. (You can also use the Windows+arrow keys to snap windows, as well.) But there's a problem: Some apps simply won't play nice. The Weather app, for example, wanted too much space to snap neatly to a corner of my Windows 10 Surface tablet.
The Snap Assist feature isn't bad; expect it to suggest other applications in windows you already have open. But in general, there's a reason that Microsoft employees demoed Windows 10 on large, single-monitor setups: These seem to work best at the moment.
Managing Windows 10's virtual desktops
Finally, we come back to the "task view" icon on the taskbar, and the virtual desktops they help create.
Clicking the "task view" button brings up a collection of apps on top, as well as a slideshow view of different virtual desktops on the bottom. A virtual desktop is nothing more than a screenful of snapped apps. One Microsoft executive described it as a poor man's multimonitor setup, with users switching back and forth between these virtual screens of collected apps. Clicking a virtual desktop navigates to it, or you can type CTRL+WIN+ the right or left arrow, where WIN stands for the Windows key. You can also click the application on top, and jump directly to that desktop, and that app.
Creating a desktop, however, is still somewhat frustrating. Filling a single screen is easy enough, as you can open up an Internet Explorer window, for example, snap it to the right, and open up Xbox Music next to it.
But let's say you go a little crazy, open up a number of windows, then want to organize them into virtual desktops afterward. Once a window is opened in one virtual desktop, there's no way, apparently, to shift it to another. It seems like your best bet is open a second desktop, then try and open up another instance of the app inside that desktop. (To open a second, separate browser window, for example, right-click the Internet Explorer icon.)
But swiping in from the left, which showed your recently opened apps in Windows 8, now shows all your open apps, not your most recent ones. That may annoy some of you.
How to send Windows 10 feedback to Microsoft
By now, you should have a pretty good handle on what's new in the Windows 10 Technical Preview. Feel free to keep exploring.
So far, I really haven't seen much behavior that indicates that Microsoft is actively seeking feedback. I did see one popup that vanished before I could click on it, which may or may not have been a question. But if you do find something to complain or comment about, make sure you use the Windows Feedback app (Click the Windows button, then type "Windows Feedback" to access the app.)
I haven't run into any showstopping bugs. I've loaded a few apps, connected an Xbox controller and played a game I downloaded from Steam. And, hey, Netflix works.
As Microsoft has said previously, this is a "build" of Windows 10. Microsoft still has nine months or so until the final release. Hopefully this gives you a sense of what works in Windows 10, and how to make it better. What's next is up to you--explore Windows 10, discover how it works, and if you find some aspect you dislike, let Microsoft know. There's still time to make Windows 10 what you want.