First off you need a big enough sample on the player to be sure they are indeed betting every flop with air, they could have been lucky and hit the flop several times in a row.
Once you've got that figured out. Next step is to see if they sometimes raise. If you find they sometimes raise, then by limping in they "cap" their range (because if they only raise good
hands, the fact they limp
tells you they have more weak hands than strong ones when they limp). Capping their range means that when they limp (instead of raise), you can remove the strongest hands from their range. Therefore if they limp, a flop with more high/low cards than middle cards will be less likely to give them a made hand.
If they never raise on the other hand then flop texture becomes less relevant apart from you needing to be careful on connected or wet boards. The three strategies I'm about to write are applicable in both cases, but if their range is capped you can be more confident you are ahead on certain flops.
1) You can check raise them, so you being out of position check, they bet, and you reriase them. This will quickly send them a message to
bluff you less.
2) (this one is not something you should do often, but if you use a hud and a cbettor's fold to donk bet stat is high you can use this) You can donk bet to deny
equity to better hands that can get made on the turn and river. This is good to do with a vulnerable overpair or middle pair and will often confuse people who bluff the flop a lot in position but aren't strong players. This one should be done much less frequently than the other 2. Check raise is definitely superior. Some will say there is no point in donk betting if the c-bet guy will just cbet, but there are flop textures where they might check instead, in that case donking is a good option.
3) Another option is to "float". When you float you call their airball bet with your own nothing-hand to scare them into thinking you have something. Then when they check and show weakness you can steal the pot with a bluff or bottom pair or whatever. This is best done against players who have a high flop cbet% and a low turn cbet% (or in other words, they almost never double barrel bluff), and it saves you chips compared to check-raising (which could potentially cost you dearly in sensitive spots).
Also pay attention to whether they vary their bet size when they bluff the flop a lot. Maybe sometimes they bet small when they have it, and big when they don't, or vice versa.
You can ignore this bit if it doesn't make sense:
Also pay attention to this, if they were preflop caller (and if they are a player who sometimes 3bets preflop), see if they bet bigger on wet or connected flops with many middle cards (and smaller on dry rainbow high-low flops). This is a sign they are possibly a solid player and their betting range on wet flops is weighted towards nutted hands or strong-semibluffs. I would be more inclined to float on dry flops vs smaller bets.
Edit:
Doh, I forgot the best strategy. If they limp Pre, steal their open limp with a 4xBB raise (assuming they fold to that kind of thing). If there are two limpers make it 5xBB, if 3 limpers 6xBB. Sometimes you encounter players who are sticky preflop and will call anything to see a flop; with these guys you can add another bb to your steal size and if that doesn't work just steal with only good hands. If they fold a lot though then you should add some weaker hands into your "stealing range".
Let me know if you need me to clarify anything, I apologize if some things don't make sense, I'm half braindead from not sleeping enough last night :/
