First, check your air filter. Easy to check, cheap to replace. The darker it is, the dirtier it is, unless you are using a aftermarket specialty filter like K & N or AiRaid. Replace if dirty.
Second, use a fuel system cleaner such as Lucas Oil Fuel System Cleaner or Startron. I have used both and both work. Use as directed for 3 consecutive tanks of gas. After that, use once every 3 to 5 tanks to maintain a clean fuel system. Lucas price varies by size of the bottle, Startron is about $9 per bottle. Both will treat multiple tanks of gas.
After those two items, things get harder and more expensive.
Third, check your spark plugs. Unless you are mechanically inclined, you need a mechanically inclined person to do this. If they are dirty, burned or damaged they must be cleaned or replaced. If they are not dirty, burned or damaged, the gap should be checked and they should be re-gapped if necessary. If your vehicle has spark plug wires, check them at this time. If old and brittle or cracked, replace them.
Other things that could/should be checked: Fuel Filter, Mass Air/Mass Air Flow Sensor, Oxygen Sensor,
Best wishes on a cheap repair. :-)