If possible, you should prepare prior to Yom Kippur, much as you would prepare on Friday for a Motzaei Shabbat immersion. That way, in the rush after the fast, you would only have minimal preparations left (taking a shower, combing your hair, cleaning your teeth, and inspecting your body). Alternatively, you can leave most of the preparations for after you break the fast (remembering that you also need time to eat and the mikveh hours may be limited). It is also possible to take care of some things, such as cutting nails, on erev Yom Kippur to reduce preparation time after the fast.

If preparing beforehand, try to the best of your ability to avoid chatzitzot. Eating meat before the fast, as is customary, is permitted, so long as you take great care to clean your teeth afterwards. Unless you have a custom to the contrary, you should break the fast with a dairy meal.

G’mar chatimah tovah!