All good advise above!
One thing to add:
Perhaps try to find say 5-8 (good and “host-spread”) beta testers to help you cover more systems / hosts that you will ever have time to test in yourself.
With “good” I mean: active when asked and preferably “precise” (not sloppy in descriptions of bugs and reproduction steps). With “host-spread” I mean: try to solicit people with different hosts/platforms/systems.
And perhaps another one (I’m a sinner regarding this one, and still haven’t learned my lesson):
Sometimes, it makes sense to simply not respond within the first 30 minutes when a support question comes in, no matter how much you love your customers and hate to see them struggle.
If your time is really very limited, I think it’s fair to “let some support issues automatically solve themselves”: there seems to be a magical time period (say 4 hours or so), within which some support questions get handled by the requester himself. Note: this is only for the simple things, not real genuine “bugs” that really cause your users serious trouble, of course. You would typically get some support question, and then say 1-2 hours later a follow-up saying “never mind, I already found it myself / in the manual / in the host docs / …” (or you’d get that as a reply after you quickly wrote your support follow-up email) Depending on the number of support requests you get, this might save you some time as well. In general, I try to respond within 24 hours, and usually get quite positive feedback about my support (it would appear that bigger companies don’t always have better support, from what I sometimes hear).
Last one: if you use ZenDesk or the like, you can set up snippets of answers to insert in your (still personal!) support requests: good for the recurring ones (of course, if it’s a real bug on your end, you should go and fix it!). And you can setup reminders for support requesters so that they get notified that you have answered them and they haven’t replied your email since say 5 days. I love to know if my support actually helped solve the issue or not!
I personally don’t deal with support issues over Facebook or Twitter, but ask people to use the contact form on my website for that (which will open a Zendesk ticket).