"Он постоянно лазит по деревьям"
"Сам не знаю, зачем я лажу по развалинам разрушенных зданий."
that's how.

Grammatically the word refers to a repeated, indefinite action of climbing, maybe in different places and over a period of time. As for the lexical meaning, "подниматься" is the most general word ("to go up"), while "лазить" is specifically for climbing up and/or down (and лезть -for some specific direction and destination)