The standard SFB/SFC shipname description is usually 2-4 letters, like CA or BC or DD or whatnot. However, with some shiplist variations I've made, I use the names of the actual ships themselves, like F-Ent for an Enterprise-class ship. I've found this to be useful because if this class gets small upgrades down the road, I can just add a "+" or even a "-1". For example, the first subtype of this class would be called "F-Ent-1" which uses only 5 characters not inlcuding the "F". The shipname descriptions can handle up to 6 characters. I've found this system to be especially useful to decribe FASA ships, which almost always have 3-5 or even more sub-type variations. So, for example, a Mark I Loknar would be "F-Lok-1", a Mark 2 would be "F-Lok-2", etc.
What system do you use?