this :D I swear I can always feel/tell a really noticeable difference in my skin if I don't drink enough water and I always try to drink at least 2 litres of water a day plus making sure you get into a good cleansing routine will really help as well :)
if you have time always cleanse twice with the cleansing lotion/gel/whatever as the first time removes all the surface dirt/makeup/etc etc and the second layer sort of does a deep cleanse and gets deeper into the pores and helps clean out all the gunk that's accumulated during the day technically you only need to do this during the day and a quick wipe with cleansing wipes in the morning before you start putting makeup on is usually more than enough and then tone and moisturise obviously if you have oily skin you'll want to go for an oil free moisturiser such as simple clear skin oil balancing moisturiser :D