Continental OnePass and United Mileage Plus are both offering 50 miles per Top Guest check-in at participating airports. You simply have to register your “smart” phone with Top Guest and then use either Facebook or Four Square to make those check-ins.
The page says you need to be “at or near” select United/Continental airports, so as long as it’s within range and you’re checking in, you should be fine (no need to actually be flying that day). You should be able to check-in once per 24 hours.
Priority Club has a similar program whereby you can earn 50 points per “check-in,” so that’s an easy way to rack up 18,000+ Priority Club points per year, and the same seems to also be the case with United now. Now, Top Guest has been known to close the accounts of those that check-in every day at multiple reward-earning businesses (Hilton, Priority Club, Virgin America, etc.), so proceed with caution.
(Tip of the hat to Gary)