If you play some good shots at the beginning of the point, you should look for opportunities to move forward as the point gets longer.
The best way to make this happen is to keep shots deep and diagonal (usually crosscourt in singles). Try to keep your opponent back or get the player moving, which should result in their shots getting shorter or weaker. This will allow you to hit more balls from on or inside the baseline and also allow you to continue to move forward and take time away from your opponent.
If they have beaten you to the net, keep your shot low-this should result in a short reply or a popped up volley, which again should allow you to move in. Lobs can also be used to move forward in doubles if both opponents are already in. Once the ball is over their head and it bounces, sneak in and be ready for the weaker reply.
Use moving forward to pressure your opponent and to help give yourself a better chance to end the point.