Take them each on their own merits really.
Personally, if I see minor edits for spelling on questions <1 day old then I usually approve them. They're unlikely to impact the front-page of questions as new questions such as those would already be on the FP anyway. Plus such spelling improvements will improve the quality of the question anyway, which should help get some answers. Often you'll find you can also Improve the edit by adding appropriate tags to it.
However, for old, long inactive questions being edited for minor improvements I tend to reject them. Bear in mind that when something is edited it immediately bumps to the top of the front page. Are such edits worthy enough to push active questions off of the front-page and out of visibility to people?
Take each post on its own and make a decision based on the impact of the change. Edits should be an improvement, and a minor spelling change is rarely an improvement enough to warrant approval.