how to start?

I watch those around me, especially the ones in good shape. :-)

I started and did what I was comfortable at. I use to only do the treadmill for that reason but now I graduated to the elliptical and sometimes the circuit weights.

A PT is expensive but even if you go once to get a routine from them it might be worth it.

Do you have friends who workout alot? Maybe they wouldn't mind showing you a few things. My trainer is my best friend, when I started this journey at the beginning of the year he wanted to help me. He has seen my highest of highs and lowest of lows (I swear to you the first day I couldn't run for a whole minute...not 1 minute.) He does it for no pay, and only asks that I give it my full effort everytime. That's it. Like he always says "I will never cheat you, don't you dare cheat yourself." perhaps a friend of yours likes to work out and would like a partner? It really helps. And yes, trainers can be so expensive!! If I didn't have my friend I'd never be able to afford one.

The internet is your best friend. The workout is not going to be a huge deal, as a new lifter you will see gains on any reasonable program. I would go with something simple and well laid out like a 5x5 variation or Jim Wendler's 5/3/1. You can also find some good bodybuilding focused ones on bodybuilding.com. The key is proper form, take the time to find videos on proper form for every exercise laid out in whichever program you choose to do.