Locating Earlyvangelist?

How can I locate a set of good earlyvangelist for my SaaS application prior to building the application?

Is there a specific way to find or locate them and finally engage them?

Thanks.

Your question seems to be based on faulty assumptions.

Here's the sequence of events that happens in real world:

• you build a (great) product
• people find it useful
• they tell others about it (i.e. evangelize)

You want to find people who'll evangelize a product that doesn't exist.

Those people do not exist.

To put it differently: the job one could call "evangelizing" (after taking enough of a poetic license) of a product that doesn't exist is the job of your sales and marketing team.

Finally, even if you have a great product, evangelization is driven not by you but by your users. Apple doesn't find people to rave about iPhone - people rave about iPhone because it's a great product.

You can try to jumpstart evangelization process using the usual methods. That's why companies advertise and send free products to influential sites like The Verge for review. It's expensive and doesn't guarantee results (to stick with phone analogy, see how poorly Nokia does despite millions spent on advertising).