Dining for miles is one of the easy and free ways you can rack up points. Register, use your credit card when you dine out, and if it happens to be at a participating restaurant you’ll earn miles automatically.
Through April 10 you can get 1000 miles just for registering to earn United miles for your dines. The best I’ve seen offered before a couple of times is 500 for joining. And if you haven’t taken advantage of it yet you should — there’s no reason not to. Plus tthere’s 500 additional miles for each of your first 5 dines of $25 or more (including tax and tip).