At the outset of my work with clients, I always remind them that not everyone can be funny. There is a false impression that a good toast has to be funny, but that's not true. If you base your wedding speech idea around heartfelt memories that paint the subject positively, that can be more meaningful than a good roast. It's about the stories and what they say about your relationship.
But if you decide to go for humor, be prepared that not all your jokes will land. Look at my wedding toast example. During that wedding speech - about 2:45 into the video - I told a joke about an airline strike in Ireland that completely bombed. Barely anyone laughed, and I had to move on. But that's just it, if you're joke bombs, stay the course.
That's where practice comes in handy. Before any speech - personal or professional - I practice my delivery numerous times. Practice will help you capture the tone, the speed, and pause points. Use your private time for practice. For example, I always go over my speeches in the shower. If you work with Wedding Speech Pros, we'll give you time to practice your delivery.
May sure that you have the first minute of your wedding speech down cold. Slight memorization helps you get over the nervousness and get into the flow.
Be yourself, don't force humor.