You might try:
take the pt's pulse first--if the pt has a weak pulse, this may mean their BP sounds will also be weaker, as opposed to a bounding pulse (best ones to practice on
using a good stethoscope (i can't hear a thing with the cheapies) and tap the bell gently first to make sure you can hear
be careful to place the cuff over the artery
get the cuff on snugly enough
ask the pt. to "drop" the arm--I tell Pt: "OK< just let your arm fall & don't try to hold it up for me", as tense muscles interfere with the sounds.
pump the cuff to about 180 and let it off SLOWLY
remember, each time you pump the cuff up within a 15-minute period will raise the BP, so try to get it the first time. if not, try the other arm.
Practice, practice, practice
you can do it!