Control the receive
I was watching some beginning/intermediate players in a tournament yesterday and noticed a huge number of points decided by the receive. Either the receiver was way too aggressive (and so made mistake after mistake) or was way too passive (and kept pushing topspin and sidespin serves off the end or side). While it's usually best to learn to play aggressive, receive is all about control, about consistently taking the initiative away from the server. If you can force a neutral rally on the opponent's serve and win half the points, you should win the match when you serve.
How do you control the serve? At the beginning/intermediate level you should focus on one thing only: is the serve backspin or not backspin? If the serve has backspin (including sidespin backspin), then you mostly push it back, though you can also loop it. If it's not backspin (i.e. sidespin or topspin serves), then you use your regular topspin shots, i.e. backhand and forehand drives (or perhaps loops, if you can do that). No-spin serves you can handle either way.
At higher levels you might want to do more with the receive, but...