To answer that, you have to look at what are you trying to improve in your golf game.
And equally as important, is why you are trying to improve that part of your game.
Do not believe all the hype about the latest golf teaching aid fads.
The advertisers are trying to get you to buy these expensive bits, and pieces, when really you could manage without them!
Ok, lets get down to the nitty gritty of this, why do you want to buy a training aid, when there are several items all around you, that will help.
What you may ask?
Well lets take your golf bag for instance.
Golf Training Aid to 'Stop Slicing'
Take a golf ball and put it down as if you are about to hit it.
Place your golf bag beyond the golf ball about 4inches further away from your body. The bag should lie along the same parallel line to the target, as you would a golf club to give you the correct alignment.
Take your normal stance.
Take your normal swing, but this time on your downswing, try not to hit the golf bag. This will keep your golf club swing path coming from the inside, and not an out to in, which is the cause of a slice shot.
As you get better, bring the golf bag a little closer to the ball but still parallel to your target.
You will be amazed at how much better your swing path will be, and will in turn cure the dreaded slice.
Golf Training Aid to give 'Added Power'
Place your golf bag against your leading leg. If you are right handed then this will be your left leg.
Now take your normal swing, and feel the bag give you some resistance as you strike the ball and go through with your body.
This feeling of resistance on your front leg(left leg)promotes the power hit.
Golf Training Aid to create a 'Good Swing Path'
Place a golf club on the ground parallel to your target, where your golf ball would normall be.
Put a tee peg in the grip end of a golf club, that you are going to swing with.
Take your normal stance and swing the club with the tee peg in the grip.
A good swing path is, when the arms are parallel with the ground on the backswing, the tee peg will be pointing to the club on the ground.
Conversely, on the follow through, when your arms again reach the position of being parallel to the ground, then the tee peg should be pointing to the club on the ground.
Practice reaching these points and your mind will soon get the correct path.
Simple isn't it!
Golf Training Aid to give you 'Better Balance'
Take 2 house bricks and place them on the ground about the width of your shoulders apart.
Now take a golf club and stand on the bricks. Put your weight slightly forward towards your toes.
Swing your golf club normally, and try not to fall over.
This will vastly improve your balance and tempo.
Golf Training Aid for 'Judging Distance'
Stick an umbrella open, and upside down, about 25 yards away from you.
Take your lob wedge and practice hitting nice high soft wedges into the upturned umbrella.
Once you have practiced several shots there, move the umbrella out another 10 yards, and try again.
Keep moving out until you no longer can comfortably reach with your wedge.
Pace off the distances of each of these positions and note the height of your backswing during the different practice positions.
This will definitely sharpen up your short game.
Golf Training Aid for improving 'Hand Speed'
Take your golf club and grip it the other way round so the grip is facing towards the ball area.
With your normal stance swing the club with an even tempo, but try to get the sound of the swish louder each time you swing.
This is like the flick that is needed to crack a bull whip.
It is this flick of the hand through the ball that gives you faster hand speed.
Try it out for a few weeks, and you will amaze yourself, how much more hand speed you will create.