I'm often asked what my style of design is. It's a bit of a pat answer to say "your style," but it's not far off.
After all, no landscape designer worth their soil is so inflexible they can't work with more than one kind of client or architecture. And a really good designer will be part researcher, part psychologist and part psychic as well, so that we know our client really well -- so well that we can deliver unique ideas and solutions that may be unexpected but are never unwelcome.
So how can you know whether a given landscape designer is a good fit for your property?
1. Don't pick an "English country" designer just because you have a Tudor-style home. Even if there were designers who specialized exclusively in one genre like this, you'd probably get the same palette of plants and cookie-cutter look as their last customer. (The notable exception may be designers such as Indig Design who specialize in native plant communities... not an aesthetic style as much as an ecological one.)
2. Unless you give very clear-cut and detailed direction, don't put too much stock in the designer who, on first sight, knows "exactly how" they would design your garden. Intuition and vision are wonderful, and certainly first impressions last. But anyone who weds themselves to a single idea without doing a bit of reconaissance on your property and developing alternative designs is missing the details that will make your garden truly yours over the long term.
(2b. If you do have very clear-cut and detailed direction, you may want to simply hire a contractor and skip the design phase. You'll have more money to allocate to construction, and you'll be able to move forward with your project faster.)
3. Don't pick the designer with the biggest ad in the phone book or at the top of the search engine ads. That's only an indicator of how much advertising they need to do; it tells you nothing about the process or quality of their work.
4. Do retain the designer that your friends, neighbors, or trusted associates are raving about. Even if their home looks nothing like yours, the raves probably are for how the designer handled the project -- process, fees, attention to detail, communication -- as much as for the finished look. Websites like Yelp can be helpful here as well.
5. Do retain the designer who asks about and understands your budget -- and agrees to work with you anyway. If you have $100,000 - $250,000 to spend on your landscaping, you'll want to make sure you interview designers who are accustomed to budgets (or properties) that size. On the other hand, if you have 1/10 that amount to spend, you'll want to talk with the designer who knows how to make $25,000 look like a million bucks.
6. Do retain the designer who "feels right" to you, regardless of budget or style. You'll be working closely with this person on myriad details, and s/he will need to interpret your wishes, dislikes and personality. If their references check out, if they have creative and practical ideas to offer while respecting your own, if they know their stuff and can communicate it clearly in pictures and/or words, and most importantly if you feel comfortable talking and exchanging ideas with them, that designer will probably be a joy to work with... and your new garden will be a joy to live in.