Putting is difficult. It's even more difficult when you have a problem aiming. Find out if you have a problem aiming by doing this simple drill.
Lay a metal tape measure on the ground. Tape a dime at one end, and then 20 feet away, a piece of masking tape exactly perpendicular to the tape measure (you may wish to use a t-square). You've created a perfectly straight putt with an alignment aid.
Remove the tape measure and set your putter on the perpendicular piece of masking tape. Cover the dime with a towel. Have a friend place golf balls on what you imagine is the line from your putter to the dime 6 feet, 12 feet, and 18 feet from you. Remain in your putting stance the whole time, instructing your friend to move balls left or right. Remove the towel and check your aim: are you left? Right? Dead on the line with each of the balls?
Aim, according to Dave Pelz, is the first fundamental of putting. Find out more about Dave Pelz at pelzgolf.com. If you're really serious about your aiming, check out the LazrAimer. Only $459! (C'mon, you're not that serious, are you?)