Like Joe said in his comment, the ideal strategy depends largely on your level. That said, I can offer in general what I think about when trying to take advantage second serves.
Some things I consider:
The Situation: This plays a large role in how aggressively I try to play someone's second serve. If I'm up multiple break points (say from the server's perspective its 0-40 or 15-40) then I tend play a little freer. If I've found that break points haven't been that hard to come by so far in the match, I might even go for a winner right off the return. Even if I miss then I still plant a seed of doubt in my opponents mind that the next time they need to hit a second serve that I might go for a winner again.
On the other hand, if it is 30-40 and this is the first break point I've had the entire match, I'll play a bit more conservatively. By conservatively I mean that I'll still go after the return, but I might just try to rip it down-the-middle or cross-court and work the point from then on. A deep return towards the server's feet can often be quite effective at generating a short ball, which might be easier to attack than my opponent's second serve.
The Serve Quality of my Opponent: This is a big variable in the equation as well. If I find that my opponent has a very predictable second serve (e.g. they always try to kick it to my backhand, or they always just spin it in to the middle of the box) then I tend to be very aggressive with my returns (regardless of the situation). The reason is that if their serve is predictable, even if I miss a few returns in the beginning, I'll eventually develop a rhythm and start making more.
More advanced players will have the confidence to place their second serves and vary their location -- when they are able to do this it is much harder to develop a rhythm; for that reason I tend to be more conservative against players who show the ability to place their second serve (because I can't, say, on the deuce side, sit on looking to run around my backhand and rip a forehand, because they might serve out wide to my forehand).
Although even in the case when players can vary their second serve location, sometimes it is possible to read where they are hitting it based on their toss (e.g. some players telegraph that they are hitting a wide serve by tossing the ball farther toward the doubles alley). Against players whose serves I can read, I again am fairly aggressive.
My Own Confidence That Day: This is the obvious wildcard in all of this. If I'm feeling comfortable with my forehand, I might swing a little freer on returns. In general if you are feeling comfortable it is a good idea to disrupt your opponent's rhythm by hitting aggressive returns. Some days, however, I find it hard to get a rhythm, so I might just roll the return in and try to get in a rally to try and generate some rhythm for myself; hopefully then my confidence will improve.
