How do I stop my cat from urinating on the bed?

Two words: Water Pistol!

Works wonders for naughty cats. Just as you catch him in the act spray him with the water. Should only take him a couple of times to work it out.

He may have crystals built up in his urinary tract as well. High magnesium levels in dry and wet cat food will create these. Brown urine is a good indicator. You can buy the expensive brands, however I've changed mine to Tuna & Egg flavor of 9 Lives...it's less expensive than the special formulas. Relatively cheap at Family Dollar stores (3.35 for 4 lbs.) if you have those in your area. Also eliminate fish flavored canned foods.

Since he is 11 the occurrence of a urinary tract infection is quite common. You can't really do much until you rule this out. Treating an infection as a behavioral problem will ruin your relationship with your cat.

Put him outside and keep the door and cat flap closed! He will soon realise where to do his business!