My advice would be is to openly ask for help.
In my experience people in the gym are more than willing to help you out. Some even go too far and offer you unsolicited advice :)
Basically, don't go to the gym and pretend to know more than you really do. Don't try to impress anyone. Know your limits. Be modest, ask for help and you'll be fine.
I totally agree with this advice. Oh and always wipe down the equipment you've been using and things should be fine.