The most helpful thing you can do is to write to your MP. This works best if you use your own words, rather than a circular or form letter.
If you’re planning to write to your MP or peers, ministers, etc, remember that these people represent you. If they’re backing legislation – especially if it’s legislation you don’t agree with – it’s their job to explain themselves.
So it’s not enough for them to simply register their disagreement with you. They have to explain why they do. When they give justifications, see if the justifications work. (For counter-arguments see false/misleading claims and Government’s justifications ).
If the justifications don’t work, remember you have the right to ask further questions. If you do, they have to take you seriously. They might find it a chore, but at the end of the day they work for you. You have the right to expect adequate answers to your questions, and it’s their obligation to provide them.