First Job in a professional kitchen, what to expect...

I myself am a Culinary Student at present.  I just completed a class this spring called Bistro, where students run a restaurant, completely student run, FOH and BOH.  This is the only experience I have in a commercial kitchen with high volume.  I can tell you to look for shoes that will give you not only support, but that you can have jel inserts (we had 13 hour shifts where we only sat down for 1/2 hour for family meal at noon and before we cleaned for the night at 10pm or so) but also not skid surface.  The kitchen floors can get slippery quick.  As far as the clothes, ChefWear is a good thing.  Just a regular chefs jacket, elastic waist pants (for comfort) and definetly something around your head for sweat, you'll do a ton of that. Oh a 4 way apron is good, you can flip it over to another side if it gets really nasty looking during the day. You will also want a good quality knife kit, chef's knife, filet, pearing, slicing, a good honing steel and a good pair of shears, any other knives you feel you like, but basically that's it.  Make sure they are sharp, believe me, you will know when they start to dull, use your steel often and keep them sharp.  About the only other thing I can think of is a nice insulated cup of some sort with a straw (depending on health codes in your area you might be allowed to keep a cup with a cover and straw on your line if it's placed below the line), you will need to keep hydrated.

Just remember the routine, when you come in, it's sanitize your area, prep, hold you items and prepare for service accordingly and don't forget about sanitation and food prep/holding rules.  You might want to look into that, temp danger zone, holding temps, procedures for storage/holding food.  You don't want a food borne illness to erupt or a health inspector to visit and you're unaware of regulations. 

That's about all I can think of...good luck

Expect hell, because that's what working in a kitchen is. I honestly could never see myself starting this career so late, but more power to you.Expect long shifts on your feet, in heat, constant heat. Non-slip shoes with nice support, such as Crocs or Dr. Schoells. 

There are a lot of "chef" lines of clothing. Until then some pants and a shirt, an apron, as you will get dirty. Always remember your Mi's. 

Cooking at home or for parties of friends, is very different than cooking in restaurants, even if its 40 friends your cooking for. Keep an open mind because as you will shortly find out, it is a whole different animal.

Quick, clean, quality. 

Never forget, you wouldn't be doing this if you didn't want too. 

good luck