If you’re having to put way too much effort in going from gear to gear, then consider replacing your cable and housing.
First step is to get a derailleur cable and housing. Most bike shops sell a cable for about $3-$10 (depending on brand and type). Housing is around $2.00 per foot. Best thing to do before going to the shop is measure how much housing you need. Obviously the rear derailleur will need more, I usually guestimate about 3-3.5 feet of housing for my bikes.
Don’t forget to buy some cable ferrules. Usually derailleur cables are 4mm thick, so that means get a 4mm ferrule.
You’ll also need some caps to prevent your freshly cut cables from fraying. Those will run you about $.10 a piece.
All you’ll really need for tools is a good set of cable cutters like this one from PricePoint.com
Other than that, just follow the routing of your old cable/housing, cut the housing to the same lengths as the old ones, place your ferrules at the end of each portion, add a bit of wax lubricant to the cable before inserting it, and you’re all set.