1) Who is the audience for your site?
Are you targeting a newer, younger audience? Then yes, flat design is probably a great fit. If you’re targeting senior citizens, they may not be as familiar with various digital interfaces and may not be as quick to pick up the non-analogical cue of your flat design elements (think buttons that look like physical buttons you would push in). However, it’s important to note that no matter where your target audience falls along the spectrum, EVERYONE appreciates a well-designed site.
2) What are you selling?
Flat design emphasizes minimalism. Which can be great, especially with the rise of mobile devices and users’ preference for these devices over desktops. However, is a minimal design a little too minimal for your product or service? For some who may sell complicated or detail oriented products (think healthcare products or services), going the minimal route may not be the best strategy for your business. This is also true if your site relies heavily on content. A lot of content gets cut when you switch to a flatter design, so you’ll need to decide if your site can survive without all its content. However, sites that sell common items (especially those with a simple design themselves) will most likely benefit from flat design.
3) Is mobile part of your strategy?
Part of what makes flat design so appealing is how well it integrates into responsive web design. Building sites on grids for responsive design lines up perfectly (no pun intended) with some of the major design elements of flat design. Grids help keep items on your site organized, consistent, and help show visual order. Again, the minimal nature of flat design makes it a perfect candidate for flat design.