Proper boot polish, brush on with shoe brush and then get a different shoe brush and brush very vigorously off with a sort of skimming/scuffing motion.
Repeat until your boots shine. Takes time but it's the best, most long lasting way of getting a really deep gleam
I vary what I do according to how much effort I want to put in, normal saddle soap brings a good shine, you can use an instant shine stick from supermarket, Asda do a good own brand one, also proper polish, nylon tights will bring the shine up really well once you have done the main polishing!