Passive vs. active treatment
When treating your hives for varroa, you can do it either passively or actively. Whether you decide to treat passively, or actively, will largely depend on how much of your time and effort you are willing to put into it, as well as how susceptible you think your bees may be to varroa. Bees that are not fully regressed are highly susceptible to mites. You might start off actively treating, and then switch to passive treatments if you find that varroa are not that big a concern in your hives.
Treating passively means that you perform varroa treatments without monitoring mite levels in the hive either before or after treating. This is the fastest and simplest way of treating for mites and will suffice much of the time. However, if you plan to treat passively you need to realize that if a colony fails for any reason, you'll have no data to look back on, to learn from, or to help you determine whether or not the failure may have been mite related.
Treating actively means putting forth your time and effort to monitor mite levels, both before and after treating. This is done mainly for three reasons, the first being that by treating actively, you will be able to determine how well the bees are doing at combating mites on their own. The second reason is that you will be able to determine how well your treatments are working to lower mite levels, and the third reason for monitoring mite levels is that you will have the peace of mind of knowing the level of infestation going into winter and (if you monitor in the spring) into the honey flow.