Force stop Android Applications

Settings > Manage Applications> Menu button > Filter by “Running.” > Select application > Force stop

You could also try the Advanced Task Killer to manage running apps more easily.

Blacklist or Block a Phone Number

Edit that number in contacts.
Select “Send calls directly to voicemail”.
Yep, its that easy!

Update for 2.2: Settings -> Call settings -> Blacklist

How To Import Contacts Into Android Phone

Export contacts from Outlook or Outlook Express (or any other application) to csv format and then import to gmail. That should do it for most users.
If you have your contacts on an old GSM phone, you could export them on to the SIM card and then import them to your new phone.

Google Contacts

While you are there, try the “find duplicates” functionality. You can also add contacts into groups. The groups show up on your phone too after the sync.
Now on your android phone, browse to Contacts>Settings>Display options>Select “Only contacts with phones”, and also Google>Select all groups.
If you want to pull social contacts too, install the Facebook and Twitter apps from market and select to import data from all contacts. You should then see pictures and other address data added to your contacts auto magically.

How To Tell If Your Phone Is Rooted

It's a question get all the time: "Is my phone rooted? How can I tell?" Maybe you picked up your new Android phone second-hand (it's a great way to save some cash, and there are a lot of great used Android phones out there!), or the cryptic directions for rooting your particular phone seemed to forget an easy way to check if it was successful, or maybe your crazy brother was messing with it while you were in the shower.

No matter the reason, checking if your rooted is easy as pie, and is a quick introduction to a tool you might very well be using now that you've switched to the dark side and rooted your phone.

Open the Android Market and search for a terminal client. There's several free ones, and they all work great. If I was forced to recommend one, I would choose Connectbot, but any of them will work.

Open the terminal app, read through the instructions (if any) you see, and you'll be faced with a text entry prompt. If your prompt is the pound sign ( # ) -- you're rooted. If you see a dollar sign ( $ ), try entering the command "su" (without the quote marks). You might see a dialog asking for permission from the SuperUser app, which you can safely grant. If the prompt changes to the pound sign, you're rooted.

Remember, root is the boss. You can do anything while you're root, including many things that can "break" the OS and cause all sorts of trouble. Read all the guides and warnings before you try anything, and by all means ask questions in the Android Central forums!

Keyboard Shortcuts

If your Android smartphone has a physical keyboard, it also has keyboard shortcuts. And these shortcuts are customizable. The picture on the left is what you see what you press the menu button once, and then press and hold it again. You briefly get a look at the keyboard shortcuts for the top-level menu items. Want to quickly open the notifications area? Hold the menu button and press "n." Menu+p gets you to the settings.

Even better is that you can set new keyboard shortcuts, based off the search button. Go to settings>applications>quick launch, and you can set new shortcuts, or reassign the ones that are already there. (And in the case of the Motorola Droid Pro, remap the quick-launch hardware button on the right-hand side of the device.)