One way to hit a credit card minimum spend signup bonus is to put your entire six month policy on a card in one shot. I just did this with Progressive and finished off the Lufthansa card bonus I had been working on, giving me 50,000 Lufthansa miles. Progressive actually seems like they will let me pre-pay the following insurance policy if I want as well. Not paying them in full for six months actually seems crazy, they want an extra 15.7% if I do not, which works out to some astronomical interest rate (34% if I did my arithmetic correctly (((price + premium) / price) ^ (1/6))^12 = 1.34 in this case).So even if one cannot pay it off in full immediately, unless your credit card interest rate is something like 34%, than put your whole premium on a card.
There are a bunch of ways to use these LH miles, here is a ten part guide. How will I use it? Not sure yet, but two roundtrip tickets to Poland on LOT for 60k LH miles would be a good way requiring me to top off the balance with a bit of spend. I could also do two business class round trips to Alaska for 64,000 miles.
Here is my LH card, unfortunately it is down to 35k sign up at the moment: