Through 12/20, sign up for the United MileagePlus Explorer Card and get 30,000 miles after you spend $1,000 in the first 3 months. Then, get another 5,000 for adding another user in the first 2 months, and another 10,000 each calendar year in which you spend $25,000. This brings in a total of 45,000 miles, beating the promotion we saw in July by 5,000. Plus, you'll also earn 1 mile per $1 and 2 miles on United purchases. When you fly United, you'll get a free checked bag for you and a companion, priority boarding, and two free United Club passes each year. The $95 annual fee is waived for the first year, but the free checked bags more than make up for that in the years after that.