Practice Makes Progress
I have a tendency to letter with large pens, and large watercolor brushes. So one of the things I would like to practice more with is a smaller tip brush pen, like the one shown here, which is the Tombow Fudenosuke Hard Tip (the blue one) and my other faves are the Pentel Sign Brush Pens. Here I am also using Marker paper, which is nice and smooth.
A couple of tips: I find if I letter smaller, it looks better. Draw some guidelines for yourself if it helps to keep your lettering straight. Just draw a top line, and a bottom line like 1/2 inch wide, and stay between the lines when you letter. Also, warm up by doing some drills! I have a free drills worksheet on my freebies page. Hope that helps get you going!