Disclaimer: I do this for a living
I run a medium-sized datacentre, and my job is to plan new installations for anything from pizza-box servers to full mainframes. Here is a few lessons that I've learnt the hard way.
Fighting human nature
By nature people are lazy and interested in the quick fix. As soon as you compromise and let 1 'quick fix' through - it turns in to a production cable that you are then stuck with until it's time to decomission the system. Do not compromise - do it right the firs time, every time.
These are the self-laminating wrap-round labels for cabling. Label everything with at a minimum the source and destination ports (along with a patch panel port if needed). This brings 2 major benefits - when it comes time to cable everything is already planned and so you just need to follow the labels, and secondly if there is ever a problem you don't spend hours tracing where each cable runs back to.
Cable ties are fundamentally evil. Do not use cable ties. Wrapstrap is a better product (no affilitation with this product) - http://www.rapstrap.com/
Velcro is your friend. Buy in bulk. Keep a stock. At home I nail small 3" to 4" pieces at the back of each desk for instant cable management.
Check what lengths you can get from your supplier - you should have a stock of 1m to 4m patch leads at 50cm intervals as a minimum. Use the right lengths.
Establish a colour coding scheme and stick with it - colour code for primary and secondary networks, colour code for firewalls, colour code for management, colour code for uplinks to additional infrastructure. Colour coding is your best way of verifying and proving that you have full redundancy to each device.
OCD is an occupational hazard
Yes - the job will make you feel like you have premanent CDO (the letters should always be in alpabetical order) - but the first time you have a problem that you can solve in minutes instead of hours by following the general guidelines above you will be glad you have it.