if you use DEI alarms then you should get a BitWriter programmer. they cost about 80 bucks online and they give you access to extra features of the alarm and make it so much easier to program one.
my process is simple, first i find and test every wire if it is a car im not familiar with. once i know where i have to go for each connection i will mount the brain to a bench and arrange all of my wires together according to where they will go, all wires than go to about the same area i will put together and run a few bands of tape down the line to keep them neat. also i take the time to put all 12v and ground feeds together and solder them so that i only have to make one power connection inside the car.
i usually wait to wire any relays until i know where i will put them so this keeps down the amount of wire i have to hide under the dash but i will make a harness for the relays that all i have to do is cut it down to size when i get into the car. although this would probably be faster if i wired the relays too but i have a thing about being neat.
once i have the alarm prewired its off to the races, the pre wiring process might take a little bit of time but it saves you time when you get into the car because you dont have a massive birdsnest that you are constantly fighting and untangling while you are making your connections. and when you make the wires into whole harnesses like i do it also saves you time when it comes to running and hiding the wires, a few zip ties here and there and thats all it takes to make it look factory.
if you do mobile installs i would suggest an inverter and a nice soldering iron. the fastest way ive found to solder the alarm connections is to make every connection first by just wrapping the wires together where i want to connect it. then after ive tested everything ill solder it all at the same time so that im not constantly picking up and putting down the gun and waiting for it to heat up. the exception to this is that i will usually solder just the ignition harness connections first and tape them up to avoid shorting anything out. solder everything else at the same time and then tape everything at the same time, this keeps you from constantly switching out tools.
lastly i will do the hood work(hoodpin, siren, tach if i use it at all) and program the alarm and bypass. test everything a few times and its done.
if im familiar with the car im doing i can do a fully soldered remote start alarm in about 2 hours if i am going for speed, usually my time is consumed by making the install look as factory as possible but if im not too worried about how it looks then it will be faster.
of course learning all the little tricks of the equipment you are using will help out a lot too. i think the best trick i know with DEI alarms is to turn off the engine checking feature for anything newer than 2000 especially if the ignition system is totally computer controlled. this will keep you from fighting to hook up and program the tach wire. the only down side of this is that i wouldnt do this in a cold climate, i live in louisiana, because with the engine checking feature turned off the alarm wont look for tach or voltage, it only uses the crank time you set and if the car doesnt start the first time then it wont try again. this is also a helpful troubeshooting feature because it will confirm if there is a problem with the tach or voltage sense.