Which familiars can I get with improved familiar?

Question

The 3.5 feat "improved familiar" states that you can acquire familiars that are not on the standard list. It provides a table of possible familiars along with caster lvl prerequisites, alignment prerequisites, and even type prerequisites. However, it also states that your new familiar options are not limited to the provided list.

The list in the table above presents only a few possible improved familiars. Almost any creature of the same general size and power as those on the list makes a suitable familiar.

So how can I determine which familiars I can get? I have seen familiar guides and handbooks that mentioned getting hippogriffs for example, which are not at all the "general size and power" of a Shocker Lizard. None of these guides seem to have a familiar with a caster-level prereq higher than 7, aside from familiars for which you need other feats alltogether.

So, how do I determine which creatures can become my familiar due to the improved familiar feat, and what their caster lvl prerequisite is?

Answer 1

The text will say if a creature can be an improved familiar

There's no trick or secret to determining whether or not a creature can become an improved familiar but simply a long slog through multiple sources. That is, a text will say if a creature can be picked as an improved familiar, and that text will also have the requirements that must be met to pick that familiar.

If you want to make a list, you don't have to do it without help. For example, the Giant in the Playground thread "Complete list of possible Familiar" (Feb. 2011) is—despite a software update rendering its table difficult to read—a good place to start, having about 90 improved familiar entries. (My own notes says there are 20 more scattered about, but, really, 90 is enough.)

In particular, a hippogriff (Monster Manual 152) can be taken as an improved familiar by a creature with a somewhere-around-neutral alignment who has an arcane caster level of at least 7 and—as an additional requirement—a base attack bonus of +7 (Complete Warrior 100).