Hi there,
Well done! This is hard work, but so worthwhile, if you're able to keep it up, and have a supportive workplace.
Gear
I had a little wheelie bag (just a normal little work one I was given one Christmas) that I kept all my stuff in: my pump (I absolutely recommend getting a manual if you can afford it: I got the Avent one, which was cheapest at Chemist Warehouse when I got mine ... best $130 odd that I've ever spent), cups and lids, a microwave steriliser (which is a great thing to use to rest the pieces on to air dry even if you don't sterilise them!), a BUNCH of paper towelling, a little book of pictures of your baby (which apparently help stimulate milk let down), a big bottle of water to drink or a thermos to make a hot drink in, if you prefer, a pack of biscuits of muesli bars or apple or something to snack on, a book to read if you like, notepad and paper (you never know what thoughts come to mind when you have a spare 10 minutes to think about your baby...), a cloth nappy or hand towel or something (to protect your work clothes against leakage), spare breast pads, spare bra and top (in case of really bad leakage), actual pads (just in case! you never know!) and some people also use rubber/silicone gloves to protect your hands, when washing the pump etc with hot hot water (I tended to just use my hands and paper towel).
I often would also take my diary (record book, not journal) and I'd write down how much I pumped, as a good reinforcer for myself ... it's hard work, and it's good to show yourself how well you're doing for your baby.
I also took a little esky, and if you freeze your milk rather than leaving them in cups, then transfer into the bags at work, so you can wash the cups and lids and leave them there. You can buy specific little ones for this, but any esky is good. I also kept a prima or two in the freezer, so on hot days, I'd chuck a rock solid frozen prima in the esky with them to make sure it keeps cool on the long commute home.
Times
As much as possible, pump whenever you'd feed. More, if you can. You can't always pump as much as your bub would drink, because they're so much more efficient than a pump ... even a magical electric pump with wings. I personally also pump extra in the morning and at night to make sure I have enough - but you'll need to figure out what is feasible for you, with the support time and energy you personally have.
You'll also find out what your workplace is required to let you do, and what they will let you do. Eg: I pump twice a day at work, but it probably takes me closer to an hour each time. Sometimes, I need to do a third extra quick pump, otherwise my breasts will explode in all their milky glory ... but I can work through lunch or back late or start early or whatever, to make up that extra time. Some places are stricter on the 30 minute rule (or whatever it is).
For the 4pm feed - this would depend on how full I am, and how far it is from work to home. I would do a full pump if there was any risk of getting blocked ducts or mastitis or anything. But if there wasn't, then I'd do a quick smart pump, and race home and finish it in person
Check with the ABA, but I've been told that most women pump 80% of the pump in the first 10 minutes - I'm not sure whether that's per side or what. It wasn't accurate for me personally, but maybe you'll find that works for you? If I had to keep it short, I'd do a quick pump from both sides, rather than draining one and leaving the other. But check with the ABA.
Making it easier and more efficient
Get yourself in the mood as quickly as possible ... know your surroundings - can you make them quiet and a little dark and secluded so your warm and comfortable, so you can be thinking about your bubba, and thinking milky thoughts? Can you put your legs up, and take a great big drink? Do you have easy access to a power point if you're using an electric one (I got someone to move a big desk for me and put an extension cord into the wall, draped over the front, so I could just walk in, close the door, and plug my pump in right on top of the desk) and have everything right there ...
Get a system in place.
Know where you're going to put your milk, when you're going to get it, how you're going to clean your gear ... feel perfectly comfortable with it (I got some weird questions from curious people - not at all malicious, just bizarre queries from people who'd never been exposed it it ) ... how you'll respond if you get ... interrupted ... etc. It may never come up, but if you've turned your mind to it, it might be a bit easier if it happens.
Drink heaps of water. Last thing you need is dehydration
Other stuff
Be prepared for lots of extended suckling/snuggling sessions, when you're back at work ... I'm sure you've already thought about that, though! I found that having a bath with DS when I get home was a good way to catch up on missed skin-to-skin time.
And be kind to yourself ...
That's all I can think of right now.
Feel free to ask more questions.