if you feel the hard round body part at the top of your abdomen, holding on either side with your hands and moving your hands back and forth, does it seem a little wobbly and moveable? if so, it is most probably a head. it's called "belottable", that wobbly feeling. a butt doesn't do that, since there is no joint to wobble around. that's how a mw or dr. could check for position, and it's easy to check on yourself, doesn't harm the baby.
as for when the baby engages, it really depends. in a first baby, could happen a mo. or more ahead of time, in a subsequent pregnancies, could wait until active labor. but, as we all know, everyone is different. size of baby, size of pelvis, preference of baby, uterine and ab tone all play a part in this.
hands and knees yoga positions such as the cat (curling your spine and tucking your pelvis), lying on an ironing board propped against something like a couch with feet at the high end for no more than about 5 mins. at a time, playing nice music down low by your pubic bone, doing summersalts in a swimming pool, the webster chiropractic technique, chinese medicine moxibustion by the baby toe of the mother, letting go of fears and negativity and spending time focused on baby asking them to move head down, all these things can help turn a breech that wants to turn. external versions can work too, but require a very skilled dr. or midwife to perform them, and can be painful to some women, as well as requiring monitoring of baby (to make sure they don't compress the cord accidently).
not to hijak the thread, but did you (or anyone who wants to answer) ever feel movement at the top and bottom in the same period of time? I'm about 30w, and I swear this little one loves to move her arms as much as her legs. it's like a party in there, and though I can't rule out twins completely, since I haven't had any ultrasounds, I measure right on for dates, and actually look a little small compared to most people, so I don't think that's it.
er, sorry for the novel length post, hope the info helps.