what exactly do you mean? i will try to give a basic explanation of their uses and such, if you have questions please let me know.
each cancel takes a charge, so make sure you have one stored up!
up b/extreme speed/ES cancelling: input up B, then press A to cancel. it can be cancelled any time before the animation ends. lucario does a little stall in the air sort of like his up taunt, and you can do anything out of this except another ES unless your first ES was grounded. it can be used to assist recovering (cancel > air dodge to grab the ledge or land on stage, or cancel > down b), or following up a combo (dtilt at higher %s > chase with ES > cancel > nair/uair/bair to kill), or even approaching sometimes (approach with ES > cancel > start your combo. i like jab > jab > ftilt > FP) but this can be pretty punishable so be careful.
down b/double team/DT is amazing for a lot of things. input down B, then any A move or hit the C stick for a smash attack to cancel. he will carry some momentum depending on the move used and at what point in the animation you cancel DT. i use it most for recovery or cancelling into smashes. for recovery my favourites are DT > nair or DT > dair. nair sends you whirling back to the stage and covers a huge distance. dair doesn't send you as far. it can be used for approach as well, like DT > dtilt or DT > jab and then start a combo from that.
does that help at all?