A good question and one asked on Twitter earlier today. I can’t speak for any other company, any other creator, but here’s my perspective about what makes for a good playtest.
Response rates when you ask someone to playtest are fucking pitiful. The best thing, of all things, that you can do is to actually stand up and offer to playtest and not just so you get a preview or a free copy of the game.
2. Actually do the Playtest
Lots of people volunteer but never actually give you any damn feedback. They’re just in it for the free game or the early access. If you volunteer to playtest, playtest. If you can’t get a game organised in time at least read through the document and raise areas where there’s a lack of clarity or other foreseeable issues. All feedback helps.
3. Play the Game as you Would Normally
For your first couple of playtest sessions just get your group together and play as you normally would. Every group plays differently and provided enough people play in their own way and send the reports back that’ll cover some ground. Games have to stand up to normal play more than anything else.
4. Then, stretch it.
Once you’ve run a couple of playtest sessions of normal play it might be worth, then, pushing the boundaries of the system. More powerful characters, less powerful characters, stronger or weaker opponents. Stretch it, see what it can do and where it can go.
5. Make Your Report Useful
Go into some detail. Give us the context. Talk about the problems specifically, not just that they suck but what you see the problem as, how it came up and so on. Frame the problem, then describe it. Offering solutions isn’t really your job, identifying problems is.