Kanji vs kana when taking fast notes?

I was scribbling notes during a group study session earlier and totally hit a wall. Usually I try to use all the right kanji because it feels more complete but when the teacher talks fast I just panic and write everything in hiragana. It gets so messy to read later! I feel like I'm losing the feel of the sentence when I skip the characters. Do you guys have a rule for when to just let the kanji go for speed?