Outside of getting a familiar that can talk out of the box, so to speak, is there any other way to get your familiar to communicate with party members other than its master?
I suppose a monkey familiar could write, but I don't think my Viper has that option...
I houseruled in my homegame that a familiar, even at level 1, could make gestures to indicate "yes," "no," and "maybe." Also a familiar can tap an extremity to indicate numbers. So...
Wizard: are there goblins down that hall?
Familiar (owl): nods yes
Wizard: how many?
Familiar (owl): taps talon against the floor four times
Wizard: are there any spellcasters with them?
Familiar (owl): shrugs wings for maybe
... and that is an actual transcript paraphrased from one of my games. Consider: a familiar, right from go, has an Int of 6. This is almost as smart as some PCs. They can perfectly understand their master and per the fluff around them are expected to be a helper in their master's studies of the arcane. For those reasons I made the ruling that I did.
In other games I've had familiars draw simple pictures or words in the dirt, write things down, or tap using Morse code. It really depends on how liberal your GM is with their rulings. FD, since you've been asking/answering questions about familiars on these boards longer than I have I trust you're running into a situation in your own game where you or another player needs to get creative?