Start by observing your current parameters. How have you been doing with nitrates, phos, alk, cal, and magnesium? And most importantly, the stability of those parameters? How are your current corals doing?
Next, keep in mind that some nems get BIG and split often when healthy. Are you prepared for that? Are you ready for anenomes to go walking around your whole tank?
Some of the most common anemones are sebaes, condys, bubble tips, and rock flower nems.