If you're building a product, prototyping is VERY important. Ideas and drawings can be a far cry from the reality of the product, and it's the only way to see those glaring issues that weren't noticeable on paper. Of course, it's also the first step to geting your product out there. 

And yet, most people go about it the wrong way. Straight from the beginning, the hardest tasks should be front-loaded. The more iterations, the better the product will be, so identify the hardest thing and start with that -- even if it means the first few prototypes will be deadbeat ugly. In fact, keeping it ugly actually protects the product's potential, as the must-have goals are being solved without directing the team off-track. 

Next, always solve for consumer experience. When negotiating with engineerings, only think about the consumer when considering product trade-offs. Because at the end of the day, there should only be a few must-haves that the product has to do, while everything else remains up in the air. 

As you or your company is gearing towards the prototyping stage, make sure you're iterating yourself towards success. Pinpoint your must-haves and most difficult tasks, don't be afraid to create ugly versions, and prototype for the right amount of time -- not too long and not too short. That way, you'll be in a much better space before you need to ship.