For diet, I found the two main things were reducing saturated fat by a lot, and eating lots of fibre.
Ignore anything you see on the Internet which says that saturated fats are fine. They certainly increase "bad" LDL cholesterol, which is certainly an indpendent risk factor for CV bad things (again despite the Internet). The UK saturated fat guidance is pretty loose & I follow the more hard-core American Heart Association recommendation of no more than 5% - 6% of calories from saturated fats. I eat about 2500 kcal per day, so that translates into a limit of about 5% X 2500 / 9 = about 14g of saturated fat per day. I generally do quite a lot less than that.
Fibre helps clear out LDL cholesterol. I eat a whole lot, 70g+ per day, and it has a notable effect on my LDL levels.
In addition, I take max dose of one of the stronger statins, Rosuvastatin, and the result is LDL at 0.8 mmol/L, a very low level.
I started at 3.2 mmol/L, and I think that low satfats + high fibre bring it down to about 2.2 mmol/L, with the statin doing the rest. But that's just a guesstimate, and the overall message is that statins are likely to have a bigger impact even than being a total satfat/LDL fanatic when it comes to diet, like me.