Reachmahjong.com

Discard both a and . (order doesn't really matter)
You should have + either or in the end
Afterwards discard a if you draw another (tenpai wait on )
or in a more likely case, discard if you draw one of these (either tenpai wait on , , or )
I'm basically forcing either a pinfu or a regular menzen tenpai with pinfu wait.

Defense-wise, I don't see anything to pay extra attention to until the locations of the are revealed.
Watch out for a yakupai dora 3 or (hopefully not) a shousangen dora 3.

Edit: A is a better discard since there's more chance of a backfire draw of what would have been a compared to .

Hmm. Keeping the 1-man brings the number of pairs to 4. However, it may actually be too late to shoot for Chiitoitsu here.

So, discard:

or

And do something else. Sadly, pinfu isn't that much of a better option here either. Now, IF Chiitoitsu is the preferred route here, then discard any non-paired tiles.