It can be good to look at the part first, don’t even pick up your instrument. Study it, see how it’s constructed, how it’s based. Is it just root/fifth?Is it triads? Blues scale. That kind of thing. What key is it in? What are the chords? Look for repetition. If it’s a repeating four bar phrase, then that’s actually only four bars you need to learn, you just need to remember how many times it repeats.