Ferrets are tough little animals and it is not hard to keep them fit and healthy. However, they can catch human colds and 'flu, so be very careful about handling your ferret if you have a cold. This could be fatal to your ferret. They can also catch canine distemper and it is a good idea to get your ferret vaccinated against this.
Damp is also a problem to ferrets. Make daily checks that all bedding is clean and dry and make sure their cage or court is well protected from the rain if it is outdoors.
Equally dangerous is heat stroke. Ferrets do not sweat, nor do they have very efficient body cooling mechanisms. Keep the cage out of fierce sunshine in the summer, and provide lots of large shallow water bowls for paddling to cool off in very hot weather. Wet towels to roll in are also appreciated. Heat exhaustion can occur in temperature in excess of 80F - not uncommon in a sunny patch of the garden.
Should your ferret become overheated, roll him in cool (not cold) water to revive him and contact your nearest vet.
Keep your ferret clean and check for fleas or ticks, especially if you take him out for walks. Some ferrets enjoy baths, but you need only bath him if he is dirty or if he needs freshening up. Ears should be inspected weekly and cleaned if there are any deposits of brown wax. There are many ear cleaning lotions on the market for puppies, kittens or rabbits. These are safe for your ferret but take care not to damnage his ears by too much probing. A corner of a tissue dampened in cleaning lotion and then wiped across the inside of his ear is all that is needed. Do not ram cotton buds into his ears.
Claws should be kept quite short to avoid catching on bedding or your clothing. Most ferrets have pale claws so it is easy to see where the blood vessel is. You can use ordinary nail clippers to clip the claw just below the blood vessel.
If your ferret seems poorly, please take him to your vet quickly. Ferrets go downhill very rapidly once ill, so there is often no time to 'wait and see'.