Instead of the simple swipe gesture to unlock your phone, you can set a custom one which can be extremely difficult for a thief to guess.
From your homescreen, go to Menu - Settings - Security. Then select Screen lock. Then chose Pattern to set one up.
It is also a good idea to untick Use visible pattern. Then if someone is watching over your shoulder while you entering your pattern, it will be harder for them to remember the pattern.
If you have forgotten your unlock pattern, then after 5 unsuccessful tries a button will appear saying 'Forgot pattern'. Press this and you will be asked to enter your Gmail username/password. The phone will then ask for a new unlock pattern. If you don't have a Gmail account, then you will have to either call your carrier or factory reset your phone.
To stop the Photo App or the Music player from indexing your files, place a blank text file called .nomedia in the folder containing your photos or music
You can use the volume buttons to put the phone in silent mode.
Keep pressing the Down volume until it reaches 0%.
If you have 'Vibration in Silent mode' turned on, it will also put the phone into Vibrate mode. To change this, go to your homescreen. Press Menu - Settings - Sound - Vibration.
If you have word prediction enabled while you are typing, you can long press the middle word that is suggested. This will bring up a menu allowing you to select various other suggested words.
There are two options to increase the font size on your phone:
The first is to simply install a new font that is larger than the default font. Font Changer and Type Fresh are two Apps that allow you to change Fonts on your phone (they do require Root access though).
The second option is to use dedicate Apps to change the font size, although they will normally only work for SMS and some Google Apps.
To enlarge the SMS font, go to the Android Market and download an App called ChompSMS. Among other things, the App allows you to increase the font size of your SMS messages.
For enlarge SMS and the standard Google Apps fonts, then download an App called SMS/Talk Text Enlarger.
If you want to conserve battery life, you can turn off the WiFi while the phone is asleep.
Go to Settings - WiFi - Advanced - Keep WiFi on during sleep.
At the bottom of each homescreen is your favourites tray, which consists of 5 icons. You can customise it by adding icons to the tray. If it's full however, you will first need to remove some.
To remove an icon, simply press and hold an icon. Then drag it to your desktop.
Then to add a new one, simply drag an icon from your homescreen to the favourites tray.
If you want to receive calls during the night, but don't want to be woken up by notifications like text messages, then you can turn notifications to silent.
Go to Settings - Sounds. Then change notifications to silent.
To create a shortcut to a website on your homescreen, go to your browser bookmarks.
Then long press on a site and select Add shortcut to Home.
Open your music and play a song. Then press Menu - Sound Effects. You will then be presented with an equalizer including presets.