To add to what LeeD has mentioned. To be honest, those shots should rarely trouble you if your preparation is correct.
You have to trust that your serving partner has the tools and nous to do the right thing. So, mostly, you expect him to pepper the returners weaker side without you even having to ask.
Let's say your partner is serving to Deuce. You should be expecting that serve to go down the T. So, your prep should be:
- be ready, maybe 1.5m to 2m back from net, fairly towards central in serve box but not quite.
- As soon as you hear him serve, you move forward at a bit of an angle and get ready to split, AT THIS STAGE YOU ARE HONING DOWN ON THE MIDDLish OF THE net.
- If your partners serve illicits that floaty shot return, your are already moving with momentum and alertness which should give you all the *punch* you need. Pop it down the hash (The percentage play), or firmly punch it forcefully anywhere. You'll have momentum with you so really there should be no fear that you're going to *wrist* punch it or anything like that.