Compensation structure generally depends on the business structure and type of product. There are almost as many ways to create a sales pay structure as there are sales people.
As for interviewing and finding the right person, I am a huge fan of having them sell me their old product, then immediately asking them to sell me on the largest competitors product (to what they used to sell), then I like to put them in front of my product and ask them to tell me about it. I expect a good sales person has already done research so they should have a clue what your product does. There are some caveats if you don't have a public website etc, so you have to work around that sometimes. If you don't have information they can learn ahead of time, you should sell them the product and let them poke holes in your sales pitch, have them play customer and ask you questions. That will tell you if they have good insights to common customer questions as well.
Hiring people that have never sold software to sell software is usually a bad way to go for your first few hires. You need industry experience and contacts.
Some more things I generally ask. Who is the person who influenced their sales process the most and how? How do they stay up on new sales methodologies? Get them to describe the difference between marketing and sales (this helps you understand how they see the team). Who is their most important contact in their rolodex that the can call on if needed? And there are a ton of other things like this.
In general when hiring sales or other non-engineering roles, the decision is about cultural fit, experience, personal attitude and of course capabilities. Remember, that you will likely go through a few sales team members before you fine one you really mesh well with that can lead your sales.