Do you have to wiggle the handle to stop your toilet from running? It's probably the flapper. Water can leak past the seal of the flapper, into the bowl, then down the drain! This can cause a real headache with your water bill. If you see the flapper deformed, or you touch it and your finger turns the color of the rubber then its time to replace it. Universal flappers are available, a popular choice is The Hornet.
If your water level in the tank is set too high it will overflow into the bowl fill tube and then down the drain. This can easily be fixed by adjusting the water level. Typically the best setting is 1/2" - 1" below the top of the fill tube. Setting this water level properly will reduce the amount of water your toilet uses, which should help with your water bill! The picture below shows a common Fluidmaster ball cock. To adjust these simply turn the threaded adjustable rod counter-clockwise. This pushes the fill valve further down and reduces the water level.
Make sure to adjust the chain from the flapper to the handle to eliminate too much slack. Be careful not to set it too tight, because this may hinder the flapper movement and you will not get a full flush!
Picking the right toilet for your house is important. You want one that is going to last for years to come. We can make suggestions and help you find one that works and fits just right. Put your worries aside. We can supply a new toilet, install and then dispose of your old one!