The answer to this will depend a little on the boat that you are sailing, so, first question, what type of boat are you sailing?
In general, I would suggest a couple thoughts here, if you are sailing a monohull (A boat with one hull) then you might try a couple things. First of all, beginners often do not sail the most optimal course up wins and so either try to pinch (point to close to the wind) or else sail a little low (too far away from the wind) when they are beating. As a result they either do not have enough speed for the turn or else they are swinging through too large an angle.
The first thing to try is to make sure that you are really sailing at the right angle to the wind. To do this pull in your sails for a beat. Do not over tighten them. You should be able to come up (turn toward the wind) a few degrees and the forward edge of the jib with get soft and just bearly begin to luff. If you fall back down (turn away from the wind) a few degrees so that softness leaves the leading edge, that should be a pretty good angle to beat at. When you go to tack, you can try gently turning away from the wind maybe 10 degrees for a couple seconds. The boat will heel a little more and will accelerate and you will feel that the helm has more force on it (weather helm) trying to make the boat tack. Take advantage of this force and greater speed, and make your tack.
Another mistake that beginners make is to turn the helm too hard over. You want to make a smooth but not necessarily hasty, turn. You don''t want to push the tiller much past 45 degrees as this creates more drag than turing force. You want to make a smooth transition from one point of sail to the other.
You also want to release the jib just as it collapses toward the center of the boat so it does not stop your forward motion.