I did my best to balance Retainers to other companion merits, like familiars and Hedge Beasts, giving them dot-based creation as seen below. They should generally be listed in the notes of the parent character's sheet, but if you really want to give them their own, you may just link another sheet instead.
Note that this is generally for material, 'this realm' creatures and people, as ghosts, spirits, hedge beasts, and similar have their own merits.
|Retainer Rating||Attribute Dots||Skill Dots||Merit Dots||Supernatural Dots|
At 1 dot, the retainer is going to be an animal or something else not fully intelligent or capable. At 2-4 dots, the retainer can only be a mortal or APPROPRIATE lesser template. At 5, they can be a full supernatural, with a Power Stat of 1. All retainers have a Morality equal to the Player Character's, for mechanical purposes.
Attribute dots are assigned with the assumption of a base rating of 1 in each, but if appropriate for a retainer type, the 'free' dot can be set to zero and then placed elsewhere. For instance, a bluebird probably has a strength of zero.
Supernatural dots can be traded for 2 merit dots, if the retainer isn't a type to have powers, or should have less than listed. Generally, they're appropriate to the PC and the retainer type.
Merit dots cannot be something that can be shared with or utilized by the PC. No Allies, Resources, magical items, other Retainers (I hate you for even considering that), Contacts, Haven/Sanctum/Hollow/Haunt, or similar. If you're not sure, ask.
Note that while Retainers are a fairly potent array of dots and capabilities, they can be killed and can't always be with you. Retainers (And for that matter, other Companion merits) are NOT protected by the no-kill rule.