Ok, I'll give you some info but not much, cause it was a lot of homework for me to get this info and I don't want to bring competition on myself, so you'll have to excuse some of the vagueness.
Biggest thing is: location, location, location!
Finding a hi sec system with a station near a 0.0 pipeline
Learning what timezone the alliances that live in that space are in helps a lot with being able to know when to be active on keeping your orders updated
Stuff to sell: Anything and everything!
First you need to figure out what you deem is a good profit margin, my general rule is, I want to make at least 100k off an item (ships more in the 500k range at least and this excludes fuels/ammo). I sell some items that have lower profit margins (like 60-70k) but have extremely high sell rates so I make up for it in volume. I do sell some items that are slow movers (like selling 2 a week) but their profit margins are extremely high (like 20-30m + )
It is all about have a variety of stuff, making yourself specialized into one type of general type of goods will come around to screw you when some douchbag decides they want to test the waters in your are and dumb a bunch of crap on the market at crap margins, it will happen and you need to ride it out so having a diverse portfolio of items to sell helps make it so you are always pulling in good profits regardless if some items got fucked cause of an asshat.
Which items to sell? Well the first way to figure this out is checking the market, start off with the basics that many different fits use regardless (example damage control unit 2). See what the prices are like and compare to Jita (should have 2 accounts for this to make it quicker with on the fly comprising, if not make a caladari alt and park it in jita and write/type stuff down and prices) and also check the sell rate for the pass 30 days to see how much of the product is moving.
Think general, you are catering to 0.0 guys mostly. Look up (if you don't know them) popular ship fits for common pvp ships and start checking prices on ALL that stuff (ship, rigs, mods, ammo, etc). Don't forget, fuels for POS and jump capable ships that will ferry in fuel from high sec.
Buy orders, use it for salvage, those 0 guys don't want to haul the shit to a large trading hub and will be happy to sell it to you. You might only make 20k-4m per item you buy but remember, with salvage you are dealing with large volumes so it makes up for itself.
Ok, so you found a spot and some items you want to sell. Don't go buck wild. Buy small amounts to test the waters. I say this cause, things might not just sell regardless of the homework put into it, or they might slower much slower than you expected. The main reason though is, to see how active the other sellers (your competition) are out there. If you find a station that has very active traders their you might be screwed depending if you are selling the same items as them or you can't put as much time into it as them. Sure things might be selling hot cakes there, but if you are getting undercut every 10 mins after modifying your order it probably wont be worth it.
When you get into this situation where you just can't compete cause competition is to stiff, you have 2 options. You can either try and find other items that they aren't selling at that station and sell off the rest of what you bought to test the waters or, and this is normally better even if it is more work, start over looking for a new location.
As for the actual hauling. If you aren't dealing with lots of big items or battleships, I highly recommend using an Orca. You can load the corp cargohold full of expensive stuff and people wont bother you flying afk cause none of that stuff drops in there if they do attack and they know it. You can fill up the ship bay with ships and even stick 1 BS into the normal cargohold if you need and you will be fine.
If you are going to stick with haul stuff under 800m (that is my personal cut off for afk in freighter) and it takes up lots of room, go with a freighter. If you are just dealing with small stuff, T2 transport with the cov ops is great as long as you are not afking it
Hopefully this helps some, if you have any questions feel free to ask, but I wont give anything super specific away