Here's a list of the methods I've used in the past and my own thoughts on them - others might add more info or disagree with what they prefer.
Apistan - chemical miticide - strips which hang in the hives for 6-8 weeks (usually in summer) when you're not collecting honey for human consumption. Can be very effective, but not in areas with miticide resistance. (becoming very common in the UK).
Apiguard/Apilife Var - Thymol-based/Organic essentail oils - gel or blocks. Has to be done in warmer weather or there isn't enough warmth to properly vaporise the oils. Less effective than miticides, but no problems with mite resistance though. Again, not done when there's honey being collected as it can taint the honey.
Oxalic Acid Trickle - oxalic acid & sugar syrup - sold pre-prepared, trickle it over the bees in winter (when there is no brood) - it attacks the mites clinging to the bees. Often done regardless of mite levels as it helps keep numbers down.
Drone brood removal - both an inspection and potential treatment method. If you put a super frame in a brood box, the bees will build drone comb all over the bottom of it. Once this is capped over take it out and uncap the larvae, and count the varroa mites. Destroying this comb will also remove a good number of mites from the hive early on in the season, keeping numbers lower for the rest of the year.
Personally, I use Apiguard when I have a high mite count, and generally always apply an oxalic acid trickle in winter, 'just in case'. Drone brood removal is also a good monitoring technique thats worth getting into the habit of doing.
Hope this helps! There's lots more methods that exist, but I think these are the most trusted and easy to implement ones that are commonly used.