Well pre-sales is a bit different to tech support, you have to hold your tongue a fair bit more, understand the commercials in a deal as you have the best idea of what kit is involved and how much time it’ll take to install and then run.
My advice is that if you are at that point in your career agencies will be calling you all the time already so its a case of letting them know you fancy something slightly different. Then at the interviews being able to give a presentation (a common test) on a technical subject but at a whole pile of levels,from the testing cust techie who wants to keep their job so will test you with outfield odd questions to the C level ones.
Avoid acronyms, spend time working out how you would explain a complex subject to someone who’s intelligent but just not in our field of expertise.
Confidence, Mojo, such knowledge in a subject that you project we can do it better than anyone else.
We have had some succss in taking L3 support guys under our wings, starting them off on day to day pre-sales type roles, for example adding another site to a customer solution, WAN circuit, QOS, Switch, WAAS, VoIP as a indvidual order. Then once they are used to that getting them doing small value RFI’s/RFP’s and then if they are up for it progressing to the larger more complex stuff.