You need to have the voice come out naturally... don't try to force your voice into something it is not. just giving you that warning.
Figure out your vocal range and get a voice coach. Very few VAs get jobs with their natural speaking voice. Try to tie a voice to a character and make a demo tape with your best voices. You best voices should be ones that can be done with consistancy and don't stress your voice too much. Also, get used to rejection.... a lot of rejection. If you can get your foot in the door, work is slow (the stage I'm in lol) but if you establish your self and are heard, it can take off.
Well, plenty of people here are looking for voice actors so take a look around this board. I know ironarm and Optimus2Primus9 both have a thread on the first page. If you're curious about equipment: If you don't mind dropping ~$80, you can get a Snowball Microphone which has excellent sound quality and alternate settings based on what type of recording you want to do. Also, download Audacity. It's a free program you can find really easily with Google, gives you unlimited time to record something (as opposed to the Sound Recorder that comes with Windows which stops recording after 1 minute) and has plenty of options to alter the sound of the recording in case you want to tweak it. Personally, I'd like it if you can get in on ironarm's series since it's only lacking two characters until the first season can start and I'm excited to work on it.
First thing's first, before you get on a mic and do voices, you need to be able to act. The key in 'voice acting' isn't the 'voice', it's the 'acting' part. Reading lines in a different voice from your own is something every Tom, Dick or Harry can do. You may not need a super complicated acting class (especially for a fan production) but that's still something really necessary to keep in mind.
excellent advice! these are robots with emotion! act in the mirror, in the shower.... act at your toy shelf. I know that sounds silly... but it all helps.
One thing I do in particular is called "Method Acting", it's basically when you kinda "invoke" the character you're trying to play, and then you don't just act, you're possessed. What're the hates, joys, favorite foods, horrible high school memories of the character, then live it out through the mic.