To exclude multiple files or directories simply specify multiple --exclude options:
rsync -a --exclude 'file1.txt' --exclude 'dir1/*' --exclude 'dir2' src_directory/ dst_directory/

If you prefer to use a single --exclude option you can list the files and directories you want to exclude in curly braces {} separated by a comma as shown below:
rsync -a --exclude={'file1.txt','dir1/*','dir2'} src_directory/ dst_directory/

If the number of the files and/or directories you want to exclude is large, instead of using multiple --exclude options you can specify the files and directories you want to exclude in a file and pass the file to the --exclude-from option.