Just want to add a few more thoughts to your post for someone who jumps into sales as their first foray:

Training: Like Dave B mentioned below, make sure the company or startup that you're looking to join has a clearly defined training program. It doesn't have be a Xerox-style month over month cycle, but it should be something that a new hire can immediately see the benefit of training after the first day. During interviews, applicants should ask company management about the training structure.

Understanding Quota: Sometimes, management places unhealthy amounts of pressure on their sales team to “meet quota” and do “whatever it takes” to get there. Quota refers to targets hit (sometimes agreements closed in a quarter, revenue earned for the year, volume of meetings per week, etc.) Depending upon the market which the company operates you're looking to join, quota could be as little as five meetings a week to hundreds of cold calls per day. Lesson here is to learn about the space you're looking to join and see what similar companies are doing.

Listen: Huge point here. I've seen a lot of salespeople rush into their pitch, explain their value proposition, tell a case study, etc. and sell and sell very hard. The customer on the other end didn't get a chance to say anything and when they did, the salesperson was in their own world, continuing to sell, while not realizing they were never listening. Sales is basically a conversation, where both sides (ideally) speak and then listen – basically, passing the ball back and forth to one another. If you don't pause, hear what the your customer is saying and listen to their points, you'll never be able to adjust your pitch to address their concerns.

Believe In What You Sell: This is one of the first things I look for when I bring on new hires to the company. I want each new hire, especially in the sales function, to believe in what we're doing, the company's vision and how their role pushes the company (and their vision) forward. Money is definitely a byproduct of hard work within the position, but you can tell a good salesperson by how strong their vision and belief is toward what their selling and therefore, the company.

Probably one of the reasons Buffett also recommends getting some sales exp: http://aliceschroeder.com/forum/topics/buffett-…

I love reading books by Joe Girard, ranked by the Guinness Book of World Records as the world's best salesman: http://en.wikipedia.org/wiki/Joe_Girard

His life story is very instructive and similar to what you notice when you read up on the backgrounds of guys like Steve Jobs, Larry Ellison, and Mark Cuban.

Nobody ever sees them coming.