It's important to make a thorough plan of your dive prior to entering the water. This should be based on an assessment of the open water conditions, waves and currents and the features of the dive site and ability of the divers. By doing this you can create a suitable dive plan - max depth, bottom time, dive objectives, turnaround point etc.
I find the best thing to do is think yourself through the dive, considering what's involved in each stage and planning appropriately.
Equipment Assembly
Buddy Check & Underwater signals review
Entering the water
Beginning you descent
Descending to depth
Exploring the bottom
Heading towards exit point / turnaround point
Ascent
Exiting the water
Regards
Koh Tao PADI Open Water course