Jeanne - thanks for asking about this. A while ago Grave-Digger, who has been inactive recently, posted up a very lengthy and expressly informative answer to your questioN.
I am doing a lot of these things when I have time; just try a few things, find a "category' with which you are comfortable and go at your own pace. If you are not sure how to handle a given case, you can make a note of the record number, and then ask for help here in the community. If you do, please give the URL ofa the record of concern. There are several of us who have done many, many corrections and are happy to help out when someone needs assistance.
I am still learning a little more every time I go in BG, and no one knows it all. So have at it. I find solving the mysteries of unmatched family groups much fun.
Will share a couple of tricks. If the cemetery is small enough, just hit browse on the cemetery page, go to the last page or so, and you will find a bunch of names that do not have surnames. By going to the transcription window and looking at adjacent photos sometimes you can match up a couple or a parent and child. Or find a duplicate with a better image. Try a few but leave them alone if you are not 99% positive of the interpretation.
I and a couple of other folks also go for the daily index shown at the bottom. At the top will be those records without surnames; those where there is an extra space in the beginning of the surname field, and those that are in various "interpretations"s of languages other than English. Sometimes, these are hard to read stones in older cemeteries or in the crowded European cems where it is not always clear what the surname is. Those you should just skip. Maybe one day someone will be camparing those with other databases and figure it out.
You can also search the daily index for misplaced Jr and Sr, and sometimese see those that are transcribe in ALLCAPS! And there are tons of typos. Fix what you can. It is all fair game.