Hitting the return of serve and following it to the net puts immediate pressure on the server.
If you are returning a second serve, especially against someone who tries to simply get the second serve in play, coming in behind the return can make their next second serve weaker, take away time on the next shot and force the server to immediately hit a passing shot or a lob at the beginning of the point. When your opponent misses the first serve, take a couple of steps forward, on or inside the baseline, if possible, and hit the return early and solid. Try returning serve straight ahead, following your shot's direction as you approach the net. This will help you cut off the angle on the opponent's attempted passing shot.
Hitting your volley short and angled towards the corner of the service box will be a great second shot most of the time. You can use this strategy on the opponent's first serve if their serve is weak or tends to get shaky during the match.
Even though the game has changed, there is still a great opportunity to use forward movement to put pressure on your opponent and alter the baseline to baseline exchange we often see in today's modern tennis point.