I did a quick google search and didn't see many (any?) reviews for the 750 non-Ti. I figured they were similar.
For overclocking stability, it's all about what you're comfortable with. What I mean by that: when I find my card's "max", I usually back off 20-40Mhz. That extra little bit isn't going to yield you much in the way of performance gains, but it could prevent an in-game crash (which isn't destructive, but is annoying).
You can run a benchmark at each clock speed. That's one method. What I've been doing is just keeping a high-intensity game running (I use BF4). Then I'll gradually increase the core clock out and continue playing (looking for any signs of artifacting or a game/system crash - it's usually just a game crash). This is a little less time-consuming, I think, but do note that I've seen instances, especially when you get to the memory overclocking portion, where I can increase the speed while the game is running and not have issues, but if I increase the speed and then load the game after, I'll get a crash. Presumably, the vram is being stressed more at load time?