There are a number of different types of Order, although they all follow this pattern, as far as they are able.
Chivalric Orders - Such as the Brevic Order or the Eagle Knights – owe their loyalty to a Country or its Ruler. It is generally accepted that a Chivalric Order should have a Sovereign Lord as its Patron. These are based on a number of RL Orders of Chivalry that were prevalent in Europe.
Religious Orders – Such as the Voices of the Spire or Balanced Scales of Abadar – who owe their loyalty a deity. They generally dedicated to one aspect of their Deity’s portfolio. They might be a Militant Order, dedicated to fighting for their God’s cause, a Hospital Order dedicated to healing and support, or something completely different - such as an Order dedicated to gathering and storing Knowledge in the name of their God (Irori?). Some of these orders might have a network of monastic buildings to support their work, others work within the normal religious systems. The catholic Curch (in particular) has sponsored a number of different orders across time. The Knights Templar and the Knights of St John are good examples.
Independent Orders – Hell Knights, Cavalier Orders, the Chevaliers and (perhaps) The Pathfinders are all independent orders who have come together in the name of an idea or concept. These Orders might not follow a strict hierarchy – for example some Cavalier Orders only recognise Knights and Members - while the Society of Chevaliers only has Knighthood as a rank. There were very few of these in real life, but they are more common in Fantasy Games.
The list below correspond to the standard ranks adopted by many RL modern Chivalric orders – However, the rank titles have been tweaked slightly to give it more of a fantasy feel, and to avoid confusion. Not all orders have all of the ranks – and some might change the name or role to suit their needs.
Patron – Most orders have a patron, who is the source of its Honour and the overall arbiter of its behaviour. The King of Brevoy is the patron of the Brevic Knights while Pharasma (or one of her Patriarchs) is patron of The Voices of the Spire
Grand Commander – The overall Commander of the Order, who is responsible to their Patron for the Order’s performance. If there is no Patron, the Grand Commander is the ultimate head of the order. A Hell Knight Lictor is a good example.
Knight-Captain - is the senior member of a Regional Chapter of an Order.
Knight-Commander - A Knight Commander leads a body of knights on the battlefield or may run a local chapter of an order.
Knight - One of the best combatants in your field and dedicated to the cause. In my worlds, this is probably BAB5 or a suitable prestige class- whichever comes first. Knights can call on their officers, and possibly the military for help.
Officer – Sometimes known as a Member. This is the basic appointment level, similar to a RL Squire. Officers are the equivalent of Veteran Soldiers, but not a member of the regular armed forces. They normally have the authority to enforce the law, call a posse together, give chase etc. They also carry out administrative duties and support their knight when called on.
Deputy - someone temporarily deputised to work with a Knight or an Officer. For example a junior squire might be appointed as a deputy while on the road. A knight responsible for an area might appoint the Sergeant in charge of a watchtower to act as his deputy.