there is a host of possible underlying causes, but i would first consider the grip. if you're right-handed, you want the club's grip in the fingers of your left hand. many amateurs hold the grip more in the palm, which is considered "weak" (open). the simplest way of describing how to hold what is a strong-to-neutral grip is to place the grip fully in the index finger (finger is naturally in a trigger position), with the grip also fully in the pinky. if all but the index finger is released from the grip, then you should still be able to hold the club without any of the grip touching the palm. the palm then naturally falls over the grip. the crease formed between the index finger and thumb will (or should) be facing your right armpit. the index finger of the right hand then grips the club just like your left index finger is, and the crease formed between the right index finger and thumb should also face your right armpit. the upper padding on the right palm just below the fingers should more or less run straight down the grip directly on the right side. the placement of your right pinky is largely preferential. some intertwine. some overlap. go with what feels natural.
the clearest description of the grip that i've read is in hogan's "five lessons," which is an awesome and quick read. he devotes a decent portion of the book to the grip... and for good reason. most problems derive from the set-up and he spends a lot of time discussing where you should be before the club even moves. for example, pushing the ball may be caused by an open shoulder and/or a closed stance (feet pointing to the right of the intended target). if your stance is closed, then you must swing over the top in order to swing at the target. probably 75% or more of right-handed bogey golfers line up to the right of the target. if you're seeing either a long(er), low ball flight to the left or a ballooned, slicing flight to the right, then you're almost assuredly swinging over the top. make sure your stance is square and that your shoulders are pointed at the target to slightly right of the target. this will promote a fuller backswing that will help you not throw your right shoulder over in order to generate power/speed.
as sort of an aside, a great visual in "five lessons" that hogan provides is imagining a pane of glass extending from the ball through your armpits and behind your body. without thinking where the clubhead is in your swing, which can be a detrimental swing-thought, focus on keeping your hands on that pane of glass to slightly under it. most slicers will throw the right shoulder over at the start of the downswing, which will result in the hands and clubhead being above the pane.
if you just work and focus on the grip, alignment, and the imaginary pane of glass, then you're well on your way to a consistent and straight flight.
All in all, I felt pretty good about my game, couple of pars, mostly bogies. I just need to find the time to play more.
Another great book is Harvey Penicks Little Red Book.
