abdominals are probably some of the most curious muscles to workout and develop. Just as every body is different, the way you abs look are different too. Some guys are genetically predisposed to having ridged abs that crate that coveted 6 pack, while others have an "ab plate" which will look flat, but never show a "6 or 8 pack"
With that in mind, there are several ab exercises. But you have to find the ones that work best for you. I do an upright ab crunch machine at the gym. It crunches both my legs and my arms together and i do 3 sets of 30 reps.
As for being embarrased to go to the gym, please don't be. Gym staff is there to answer your questions and help you understand the machines and proper weight lifting. We guys, whether we're str8 or gay, seem to feel less macho if you have to have for directions on the road or in the gym. TRust me, no one will think any less of you for asking what to in the gym. That's better than doing exercises wrong.