I've trained many STB's to canter. My family had a small breeding and racing operation and horses we retired were always retrained so they were easier to place into good homes. I took horses for other owners as well so they could be retired into riding homes. Never had one I couldn't get a consistent canter out of and often added I've a rack depending on the end goal for the horse. My current OTSTB is a trotter with a gorgeous walk, trot, rack and canter. First don't think of the canter as a "faster gait". For a OTSTB it really won't be. Especially early on when you go from a pace to a canter you'll feel the horse slow down. If you push them "faster" to get the gait your horse will be all strung out and keep falling back into the pace and not keep a good canter. This is the biggest mistake that I see when I help people with their STB's. They keep pushing their horse faster and faster to try to get the canter and they end up with a couple of strides but then they just fall back into the pace and spend the time just zooming around. Start at the walk. Work on getting balance. I especially like flexion exercises as STB's of the track are often very stiff. Once I have a horse that is balanced, flexible, and has at least very basic collection I'll work on canter. Personally I prefer walk to canter transitions. I find it is much easier to get the timing right to get the canter from the walk and it is much easier to keep the horse balanced which makes for an easier transition. I find pacers especially will make walk to canter transitions easier then pace to canter. If you aren't comfortable with walk to canter transitions get your pacer trotting consistently before working on the canter. You'll have much better luck with your transitions from the trot. Reward the canter! Even if it is a disaster or at times you really didn't intend. You can clean it up later. It is better to have 1 or 2 balanced strides in a canter then 30 strung out racy out of balance canter strides. Ask for the canter and bring it back BEFORE it falls apart. Hills can help. Weighting hind feet slightly can also help with pacers. I have a pair of weighted bells I'll use for this, but it is for real hard cases. Some people will shoe the hinds only when training a pacer, but I've never needed to try that. Do you need a saddle? No, but unless your balance and seat are fantastic a saddle will help. You need to be balanced so your horse can be balanced. You also need to ride the canter just like @manesntails said. This really works! @Faster Horses got her pacer cantering first try just by riding the canter. Since you are a trail rider I'd work on a rack instead of a canter. A rack is fantastic to ride and a perfect way to cover ground on a long ride. If you love in a state with an active Standardbred Pleasure Horse Organization I highly recommend you contact them. Everyone I've ever worked with from a SPHO has been willing to help others out.