If there is one tip about begin a Consultant that i can pass on to everyone else its this. BE PREPARED and get the customer PREPARED
Make sure when you do a site survey or discssions with a customer that you lay out all the Pre reqs up front and not go on site untill they have done them
From having a Server available to install ESX or having space on a SAN to use as shared storage (yep I have been there on site with none of these things done). Even the basic 1gb network for VMotion. its amazing the number of customers who think that they can get away with 100mb.
All these things all though really annoying for the Consultant boils down to one thing. Bad Planning. Get involved as early on in the sales process as possible and keep the salesmans feet on the ground. Dont let him promis anythign you know cant be delivered. (but NEVER contradict him in front of a customer). Get a site survey day out of the customer, make a check list of things that are needed and what yu need done. GIVE the customer his list of things to do and let him get on with it.
Make sure you concentrate on networking, Domain setup, IP addresses, switch configs, failover paths anything yo ucan think of that will screw up your day or 2 onsite
In the end YOU look good, Your company looks good and most of all when everything is in place and working perfectly VMware looks brilliant.