When I was learning ASL, I found that signing along to tv shows and videos allowed me to develop the muscle memory. Because many words (in ASL) do not have "official" signs for them, practicing fingerspelling of sentences also helped when I needed to spell out words that have no sign associated with them.
Written sign language dictionaries are useful for looking up and practicing words, but because there is no corresponding "written" part to sign languages (whether American, French, Spanish, Chinese, &c.), the suggested practice to drill the words into your mind is through visual/actual practice.
As is often repeated, practice makes perfect. So repeating the different components of the sign (which could be said to constitute its "spelling") and fingerspelling the words followed by the actual sign (for those that have them) is the closest analogue to what you do for other languages.
Additionally, recording yourself on video and watching it again is the visual equivalent of writing the words over and over. It gives you an opportunity to see how you look while signing and if you need to tweek body position, facial expressions, relative distances, and the like. It will help your movements become more fluid, because if you cannot understand yourself after watching your recording, neither will anyone else.