I am a Medic with my countries largest EMS provider (who also provides coverage @ events - which I do).
Most of the events I do are the down in the dirt, get on the back of a quad bike to get to the Pt sort of events (plays havoc with my uniform & gear but I accept that) I have found that 11 things are an absolute must when doing this sort of job.
1 – Have a excellent pair of pants, they must be, easily washed, very sturdy, have cargo pockets (expanding not flat) & must be able to accept a belt (having reinforced knees is another plus).
2 – A good comfortable, sturdy belt that will not fall apart on you while still maintaining its looks after being abused.
3 – Quality Holsters, they are a must. If possible get ones with the plastic clips not Velcro as it wears out over repeated usage. They must also have flaps to cover what is contained in them (even shears) as Murphy's Law is in full effect here, anything that you have on you that you need is likely to disappear if not strapped down (speaking from experience).
4 – A good quality multitool is needed as there will be times when you think, "Now how am I going to get this off/away/etc" & this will expand you options (reminds me of a time when a spectator get her metal bangle stuck on a tree branch – I just used the wood saw on my Leatherman wave to cut the branch or if that failed then there was the metal saw I could have used.
5 – A reliable, bright, lightweight (see #6) Light that you are comfortable using (I use a SF A2 as it gives me the option of bright light or a low level pt exam light in a KISS package plus keep at least 1 spare set of batteries on you (Murphy's Law) plus another set in your med bag (assuming you have your own bag/jump kit/etc). Also keep an AA or AAA led light with lithium batteries in it in your med bag (2 is 1 & 1 is none) preferably a medium level flood-light (that way you can have a bystander stand above you & illuminate the scene).
6 – Lots of glove on you – when the SHTF you really don't have time to go back to the truck & get more because your glove pouch/pocket etc is empty (I carry about 10 pairs in my custom pouch plus another 20 or so in my med bag)
7 – High quality boots (yes boots, not oxfords, they need ankle protection) that are comfortable, broken in, made of leather or leather/nylon (for long service life & presentation), preferably waterproof, have more than adequate cushioning as you can be resting your weight on your feet when they are on odd angles (I have prefer 8" boots as they go over your ankles & help with standing for long periods & for protection from sticks/stones/etc, they also reduce the chances of a serious ankle injury if you misstep etc).
8 – All this must be lightweight, as you will be wearing it for the entire shift. Plus when on a call/or moving to a pt you will more than likely be carrying a bag of med gear + other items which soon weights you down.
9 – Trust in your gear, you must know, where it is, how much there is of it, how it works, how to put it together/take it apart/fix it (again Murphy's Law), & also the limitations of it.
10 – An Organized med bag, it is all good to carry lots of supplies/gear in your bag but if you have to take 30 – 40 sec finding it then it may as well be useless as you may have a pt bleeding out & you can't locate your combine dressing, you must be able to find your gear/supplies very quickly, with one hand & be able to get that gear/supplies out without pulling all the rest out. Also having them in smaller bags inside your med bag reduces the chances of losing said items when it comes time to pack the bag up again.
11 – Above all else KISS
Patriot36 – While using clips is a good way to carry items with EMS, Murphy has a field day (See #3) with any unsecured equipment, straps and the likes (last year we had an incident where a medic got a dislocated shoulder from a strap catching on a branch as they went past on the back of a quad bike)
These are all my opinions based on 11 years of service and can be taken with a grain of salt.