Here are some of my experiences.
Think about what you want now and what you could want in a few years time. This is hard to sometimes get right but an example of this is laying extra conduit to the gate. We did this in my house I have 3 conduit pipes going to the front gate these go back to a junction back and then a larger conduit (its actually a 2.5" soil pipe) from there goes to the patch panel. This allow for me to put in a video entry system and wire it up to the patch panel and have a motor on the gate and still have room for something else.
You can never lay enough cable for your structured wiring system or power sockets. I have 6 RJ45 points in my lounge, and all are used. I did do it in such a way that I can add at least another 4 RJ45 sockets if I want
One of the biggest problems I have come across, this is looking at it with my installers hat on, is builders, electricians, construction companies or project managers who don't have a clue as to what you will be doing or even why you are even there.
Normally we walk them through the install process, with what goes where What it will look like when its finished and what it can do. Then I take a can of either black or fluorescent pink spray paint and mark where things have to go. And normally 90% of the time its OK. Also good communication between builder, and installer (or yourself if its the DIY route) is a must. Without it things can start to fall apart. On projects that will take weeks to months a weekly update meeting is a good idea, and also find out if other trades will be in at the same time, this can make things jobs easier to plan. On one job we had a Monday morning meeting to let people know what was going to happen and a Friday afternoon meeting to explain what had actually happened and if a job was behind schedule why it was.
Hope this helps