Great question!!
My name is Humberto Valle, I have been an entrepreneur and investor for about 10 years now. My background is in strategy and marketing and recently sold a small marketing firm I started dubbed www.Unthink.me.
Now I focus solely on consulting.
Anyway, as another expert here mentioned - the best way to learn is to be one. But there is a caveat to that and that is that a lot of newbie 'treps (as I call them) or would be treps get lured into the 'life' not really appreciating the harshness of what it could entail mainly in regards to sales and marketing.

It doesn't matter what type of business you launch, what you produce or who is your target market - the bottom line to any startup or entrepreneur is driven by sales and if you aren't comfortable selling or aren't able you will not succeed. So my suggestion would to simply start selling, either go get a job where you depend solely on sales or start your own small (humble and non-would-be-world-dominating) business where you get to sell directly to potential buyers. The way the market is heading and technology enabling this path - most jobs will eventually require customer service, tech/coding skills, and sales. Which is why naturally a lot of people are being driven to runt their own companies.