If you don't have any training at all then I suggest you start with Singing Coach Unlimited Software. It's basically going to help you get the basics of matching pitch and begin to get you familiar with singing basics.
From my own first experience with singing lessons (before I got the software) it helps to get familiar with a keyboard enough to pluck out your practice pieces, so I also recommend Piano Wizard. It's a fun game environment for learning piano easily and naturally. If you get good at the game then it will eventually teach you to read musical notation, too. (I am having trouble getting both hands to work together on the basic game so it will be awhile before I get to the reading music phase.)
If you are an experienced singer, then you should look for live coaching to get beyond the basics. I don't have any idea about costs, but you should make sure that your teacher is someone you trust. Talk with them about their methods and philosophy. You won't necessarily understand everything they say, but if you are still comfortable with them then give it a try. Pay attention to your discomfort if they dismiss any of your questions or talk down to you in any way. Don't bother with someone who can't be sympathetic to your concerns and treat you with dignity.
Church choirs are a very good resources for doing some singing, getting instruction and asking around for good coaches.
Singing Coach Unlimited Site:
Piano Wizard Site:
for a discount use this code: DBERG-11DON