The bike I ride used to run great.  Lately, it's not been running quite as smoothly - probably because we stored in outside last winter and it got rained and snowed upon.

Found this nice site on bike repair: http://www.utahmountainbiking.com/fix/.

Also, finally took a look at my bike to understand it better.  The left handle gear adjustment levers go to the front pedal gears (and left brake goes to the front wheel).  Higher number means larger radius gear.

The right handle gear adjustment levers go to the rear wheel gears (and right brake goes to the rear wheel).  Higher number means smaller radius here.

Pressing on the brake handles presses a clamp onto the wheels' rims.

I still need to understand the gear shifting mechanism better.  I tried propping the bike onto a chair and lifting the back end, so I could pedal and shift and watch at the same time but it didn't work out that well.  Maybe I can talk my husband into helping me - four hands might be more useful than two.