1. YES you can BUT it is now whether or not the card can take the push of mhz, usually they can but more often than not, it's too little to make any difference. Even higher end cards nowadays, some mhz increase doesn't give much performance boost.

2. Should you? NO, unless you just want to experience it. Low end card, boost 1 frame is still low end card performance.

3. Just do 10mhz increase until the system misbehaves, then stay at the last successful speed. *my style is straight 50mhz - 100mhz boost or more but for newbies, I think going that figure is damn scary. hehe*