Bed risers are great and a wonderful permanent solution to table height. A quick inexpensive solution if you are using a folding table: purchase 2" PVC pipe and cut it to 12" lengths. The wonderful Home Depot employee cut a 12 foot length of pipe into 12 pieces for me. Now we can quickly raise 3 tables at retreats. Much less expensive than bed risers and easily transported.
We have also used the pipes any time we do assembly line projects like a take out only fund raiser meal. Two hours of filling plates bending over the church's tables killed my back! Guess what they asked to use at the next take out only meal? We also help wrap presents at Christmas for charity groups, and stuff stockings...the list goes on....