Step 1: Go to tweeterid.com and enter your username.
Step 2: Copy your user ID from the previous website.
Step 3: Copy the following URL:
https://twitter.com/messages/compose?text=example%20text&recipient_id=1001
Step 4: Replace example%20text
with whatever you want the message to say. Your message must be ASCII-encoded. W3Schools has a reference guide that helps explains ASCII encoding (URL encoding) and even has a tool that will encode text into ASCII for you.
Step 5: Replace 1001
with the user ID you received from step 2.
Step 6: Tweet the URL you just devised to the world.
What to do you mean by CHARACTERS MUST BE ESCAPED?