My best bit of advice would be to learn and perform the responsibilities of your current rank. Get yourself and others within your clan involved in your clans activities. Attending your meetings is key.
One big thing I look for in my clan is those members that do everything possible to make new members feel at home and involved with the clan. This can be things like sending out invites to new (and older) members to get everyone together, playing and ultimately having fun.
One thing I will say though is don't be solely focused on being promoted, as chances are it will not help your clan, once you have shown the leaders within your clan that you are capable and have the drive to be successful in a higher ranking position then I'm sure they will acknowledge that.