You must URL encode any data you’ll pass on in a query string, such as a form post, or other url parameters.
I’m always having to look these up, so this article is as much for my reference as yours.
A URL encoded character is the ascii value of the character preceded with %, with a special case for <space> which is quite common.
Here are some of the most common characters.
|<space>||%20 or +|
Here is a full ascii table you can use to find the hex codes for other characters, click to enlarge it…