If you have an MP who is even mildly non-cunt, getting in touch with them to an annoying degree if you have time on top of other things. The survival instinct is strong and if enough people focus time into letters etc. they'll start shitting themselves, esp if they're a new face.
My MP is Rosie Duffield. She does not care to be accountable to her constituents, and so our best practice is probably to do what she wants done to trans people back to her (hound her out of public life).
These people don’t believe in democracy. Making sure every appearance is harassed is vital.