If you're looking for cracking customer service and brilliant products have a look at a few wedding awards websites. They will list the winners (naturally) but also tend to have a directory of the finalists too!
If the locality is important, then Google Maps is your friend. Search for suppliers who are near your home or your venue, chances are they will be familiar with your venue and their travel costs will likely be less too. Google will also provide you with insights such as reviews and images from other couples.
These can really help you to discover suppliers that are a safe pair of hands. The wedding industry is very well connected, recommendations from other wedding suppliers such as your photographer, stylist, or florist will give you an additional element of peace of mind that they have been tried and tested.
These guys will NEVER put their reputation on the line for a dodgy supplier. They will only recommend trusted suppliers for you to work with. Lots of wedding planners will have a recommended supplier list on their website that you can peruse.
This one is particularly BRILLIANT for finding photographers, florists, musicians and stylists - search for your venue's name and slight variations such as #VenueWedding or #MarriedAtVenue to find suppliers who have worked at your wedding venue in the past and examples of their work.
Overall, have fun when choosing your wedding suppliers. Make sure you have a good idea of what you are looking for but be open to ideas and suggestions from those you speak to. I always advise choosing suppliers that you really 'click' with. Ones where you feel assured that they will go above and beyond to bring your dream wedding to life, meaning you can enjoy the run-up to your big day, stress-free.