(a) Key shot:
Backhand volley drop. You have played a good deep drive to back left, it is tight and forces a fairly easy backhand volley for you. Your key reply here is front left drop, not cross-court deep which is often played. The front left is a nightmare for your opponent to deal with. He has to play it almost in front of himself, virtually always forcing an easy put-away for you. Watch the Pros - good lengths are a given. Front left is the key.
(b) Don't be afraid to retreat to absolute basics where necessary.
If your opponent hits a good tight drive, then the risk/reward calculation must be to simply hit a good tight drive back. If his next shot is a little looser, then you have more realistic options - perhaps a straight drop or you may decide that you can use this looser ball to hit an immaculate hard low drive that will force a looser reply enabling you to play an even more forcing drive or drop. But if you try anything where the risk/reward is against you, then you are probably in for a bit of running. Offence can become defence very quickly.
If the game is going against you, or if your opponent is hitting frequent winners, it is generally because you have become too loose. Retreat to absolute basics for a short while and the game will begin to fall back into place. Give him nothing to hit. "Shot players" generally do not have much patience and cannot resist playing too many short. They will do this even off your tight basics, thereby playing weaker shots allowing you to take control.
Alternatively, you could follow such often used advice as: "Hit the ball hard. If that doesn't work, hit it harder", though hopefully sanity will prevail.
(c) Back right corner.
Hit more straight. Not easy, so practise it. The naive player will "bottle out" and hit the easier cross-court first. It may be hit hard but it will be cross-court. The better player knows this and will easily cut it off and play straight drive or drop or - if he is very good - dummy drop / but drive, according to how bad the cross-court is.
(d) Bearing in mind (c) above . . .
when you play a deep straight ball on the forehand, do not go back to a position to the right of the centre line (you will be passed cross-court) unless your shot has glued to the wall and a very loose reply is obviously imminent. If anything, stand 1" off-centre to the left and be ready to deal with a cross-court. Even if it is actually hit straight, it is generally relatively easy to deal with - certainly much easier than being passed by the cross-court.
(e) As you become better tactically, you will automatically get better technically.
Don't spend too much time on technique (though as a beginner, getting the basic techniques right is a must).
It is no good hitting fantastic looking shots if they are played to the wrong areas of the court. Many players look like World Champions in the knock-up only to be horribly exposed in the game. Indeed, the flashier a player is in the knock-up, the more confident you can generally be in his weak tactical knowledge. (Also, of course, the more sun-tanned a player is, the less fit he probably is).