Electrical Tips and Tricks - Please add any you think useful

make sure you put the heatshrink on the wire (but not near the area to be heated) before you make the soldered joint.

i have made this mistake more times than i should have

haha...wise words ....we've all done it

Potentially more useful. I can't be the only one who's terrified of metalwork and welding but happy to have a go at things like wiring, though not always with brilliant results.
The opening tip has already made the whole thread a win.
I saw Edd China (divisive figure but I have genuinely learned by watching him over the years) using the interlocking wires method but they didn't show how to deal with the splaying wires. My first few attempts at this were awful.

I don't have pics to hand but I have a few of these in-line fuse holders wired up with croc-clips for extra piece of mind when I'm doing something on a car or bike I need to use to get home. Saves embarrasing phone calls to my special lady friend....

I usually find somewhere to unhook a wire and clip this on in-line.
Used them more on bikes than cars to be honest but they were really handy when I discovered the non-standard wiring colours behind the stereo of one of the W124s.

is it just me that doesnt struggle to solder wires together then? never ever seen anyone doing whats going on in the pics

Never heard of a de-pin tool but often use a tiny flat-blade screwdriver from a cheap-n-nasty toolkit to prise the barbs off the pins to dismantle the plug.

If you've never been inside of multi-plug, have a look here
blog.machanon.net/2010/05/19/180/

I've tried using a soldering iron and TBH I did get usable results. it was a pain to do and I didn't get as clean a result I do now.

Now I just use a tiny blow torch, something like a chefs blow torch, so much easier.

As an electrician the above method is fine to use but it can often make the wire quite bulky which if you've got to pull through grommets etc can be awkward or even impossible.
The neatest way IMO is to twist both ends individually, "tin" the end of the "bit" , heat the wire then simply touch the solder onto it. It should run neatly down and coat the wire. Do this to both ends, rest them ontop of each other, quickly heat it and pull the iron off the second they melt together.
This way the cable, even once heat shrunk appears pretty much the same diameter as the original.
Another top tip is to use the solder from the reel rather than melting off a smallish piece to do the job, this honestly makes it a lot easier, you can even use the reel as a "third hand" for awkward jobs.

Clever that but as said a bit pricey!!!

Already many useful tips!
Hope we'll see ideas on planning and making up project looms and sub looms, logic and safe routes (heat and damage), easy to use donor fuse boxes with maximum number of fuses to accommodate EVERYTHING inclusive of sound system components etc, stealth looms and what else is needed for security - alarms, fuel cut offs etc, calculating battery size, kill switches and/or in line battery cable fuses. Trip switches in stead of fuses, dash tell tale light for bulb failure - the list goes on!
Thanks!