Don't over tighten. It's very easy to strip a thread, you will be surprised who untight(?) some nuts are. Haynes manual will give a lot of torque figures so invest in a decent torque wrench. Generally speaking, the smaller the nut/bolt, the less you need to tighten it. Don't rush, if you are in a hurry, walk away. Don't chat on the phone to a mate/mum at the same time, you will forget something. Never leave a loose nut. If you must, leave a spanner/allen key/ socket on it to remind you. Save all your jam jars and Chinese take away boxes, put the nuts/bolts/parts in different boxes and label each box. When taking off engine cases etc, cut a piece of cardboard the same shape as the part and make holes to poke the bolts through. You will find some are 65mm some 70mm and very easy to mix. Halfords do a good range of professional tools at a reasonable price. No Snap-on, but a fraction of the cost and a lot better than Silverline. They often have sales so don't pay full price.