Practice good hygiene. Here are two simple ways. Keep a small plastic bucket and lid amongst your kit and collect all the odd bits of comb you find in the course of your inspections. As you put the hive back together (not as you take it apart!) remove the bits of brace comb, especially those that are likely to trap bees or the queen, and put them in the bucket, with all the queen cells you've cut out, the pieces of drone comb, and so on. That way you don't leave any material exposed in the apiary that other bees will rob, material which is a potential source of foul brood and other infections. It's surprising how much useful wax you can collect and recover during the course of a season too! Now that you have reduced the bee's ability to transfer infections, what about yours? If you use gloves another good habit is to use disposable latex gloves, available at a £-shop near you, over your own gloves when moving between apiaries. Not only does it keep your expensive gloves clean, it even improves the fit sometimes! If you visit another beekeeper's apiary, maybe on a garden meeting, it's just good manners to leave your dirty old gloves at home too. Borrow theirs, use disposables, or do without.