One bit of advice I'm going to pass along is to make sure you have backups available; for a 10M nothing sucks more than having one person not be able to make it and have to hit Trade looking for a pug; it hurts morale and almost always unless you're on a really good server means any progression is being halted that night.
Also, don't let friendship come in the way of success. That sounds harsh but one of the things I've consistently seen in guilds is that progression gets held back because nobody wants to tell that one guy everyone likes that he's doing poorly and has to shape up or ship out, so you deal with it and end up just another scrub guild that has barely any kills, which in turn hurts your recruitment because higher-progressed players want higher-progressed guilds (and hell most people looking for guilds usually want something a few bosses above their current progression level), and lower progressed players are often (but not always) not as skilled. It's very easy to get into a downward spiral of having low progression and then never being able to recruit good enough raiders to get past that hurdle, so you constantly have low progression and low-skill raiders.