Back when I was on a 'lower grade' laptop without Nvidia graphics, I dropped my image sizes by quite a bit (say 1280 x 720). This can speed up render times, but of course you are sacrificing a bit of quality if you were to say upsize them to 1080P afterwords.
Now that I have better hardware, I'm using the 'render at double dimensions (3840 x 2160), then reducing the size in Photoshop to 1920 x 1080 when I'm done tip (several people in Daz land like doing this). This helps offset a bit of the graininess in Iray renders. But of course it comes at the price of much longer render times. I mention this because if you are doing a 'simple' render without a lot of background or whatever, that can render in a few minutes, well the 'double the dimensions, then halve them in post trick might be useful to you occasionally...
Note that I now have dual GTX 1080s for rendering, so 3840 x 2160 isn't as painful as it would have been on the older laptop. Complex renders can still take 2 hours or more though, and even then those are not hitting 100% convergance.
Another thing you can do is, if you have two computers or if the CPU isn't getting bogged down, is to run two instances of Daz, working with the second instance on some other thing (maybe setting up a followup render with a different pose) while the first one is baking. That way, you aren't sitting there just twiddling your thumbs waiting for grass to grow...
If you are doing renders for a game, and are hardware constrained, I highly recommend using the 'render characters without background, then superimpose them on a static background in RenPy, etc.' trick. Several games/interactive novels do this. Sure, the lighting won't be 100% accurate, but rendering characters by themselves without rooms, furniture, etc. in the background that increase scene overhead can help cut down on those render times.
