hello,
do they usually ask you to do some procedures? to draw blood, to insert IV lines, or to insert a foly catheter??
if not, then when do you they ask you to do such procedures?
Totally depends on the rotation/hospital, and somewhat on your interest level. At some places you have to be a bit proactive -- if you come in saying "if the opportunity arises, can I try" some resident probably will make sure you get a shot. I definitely tried to get med students as involved as they wanted during my intern year. You absolutely should be asking to put in foleys in the OR, NG tubes, etc. As a med student I got to do I&Ds, paracentesis, joint aspirations, LPs, lots of suturing. Some places shy away from med students doing much, so I've seen med students pair up and put IVs and even NG tubes into each other. To a large extent on some rotations there will be a disconnect, where your rotation coordinator will tell you you absolutely need to do X, Y and Z, but then if you sit and wait for it to happen, it won't -- you often won't be "asked" to do the procedures. You will have to be proactive. You may even have to tell the nurses, if there's an NG or Foley to put in, page me, or else you may come up short on your procedure checklist.
Also bear in mind that first year residents start in late June/early July of each year, and so for the first month or two there will be lots of people fighting to do procedures. If you hold off on the procedural rotations until the fall, you will have a better chance to do stuff once the novelty has worn off.
It's a good idea to be proactive and do as much of this as you can during med school, because otherwise you may be learning on the job on very tough patients at 3am while on call. The nurses won't call you for the easy ones, so if you have some experience under your belt, you are much better off. If you find you aren't getting as much procedures in, an ED elective during 4th year is a good idea (although more work than many folks like to do during 4th year). Sign up for as many overnight shifts as allowed, because that's when the residents/attendings are more likely going to let you do stuff as a "reward" for being there.