Depends on how much luggage you have and how much money you're willing to spend.
I took a taxi a few times, it's fast and comfortable, costs £30.
The other option, as already said, is take the AirRail Link from the airport to the Birmingham International rail station (£0.00), train to Coventry (~£1.50-1.90) and bus to the campus (£1.50). Ten times cheaper. You can also take a taxi from Coventry station to the campus if you don't fancy getting on a bus (£9.00-£10.00).