To be promoted to Elder, we are looking to see that you will stick around, are active in the clan, and that you are thinking about the whole clan and not just yourself in clan wars.
Your need to fulfil these requirements:
Elders - invite friends, people from global etc into the clan and kick them if there is a problem that can't be solved. Do not kick people you had nothing to do with. Be cautious about accepting joining requests if you don't know who the person is, especially during prep-day or wars - they may be a spy from the enemy team!!!
[New Rule 10 Feb 2017] Elders who have not used 3 or more attacks in last 5 wars will be demoted to Member. Elders are expected to donate at least 100 troops per month.
Co-Leader promotion is more complicated. The main rule is that co-leaders are the type of people not asking to be co-leaders. If they do, it kind of suggests they don't like the way the clan is being run and might start messing with stuff when they have the power...
There'll be a right time to be promoted to Co - based on lots of things - including input from other members - but there are no fixed rules.