https://github.com/rustwasm/console_error_panic_hook
https://github.com/rustwasm/wee_alloc
https://github.com/iamcodemaker/console_log or another suitable logger implementation.
Compiling with Link Time Optimizations (LTO) and optimize of size. See https://rustwasm.github.io/book/reference/code-size.html#optimizing-builds-for-code-size
Have a look at your dependencies. Do they offer any flags to shrink their size? Are any of them big enough that calling out to JS might be worth it to remove them?
Compile wasm to JS to support IE? See https://rustwasm.github.io/docs/wasm-bindgen/examples/wasm2js.html