Script to enter text in a box Here's a little script that enters text into a document when activated.

tell application "TextEdit"
  activate
end tell
delay 0.2
tell application "System Events"
  keystroke "Hello World!"
  keystroke return
end tell


I stuck the delay in there because otherwise the first few keystrokes tend to trigger before the window is done activating, so I end up with "lo World!" in the document and "Hel" in whatever other window had focus when the script was activated. Is that the proper use of delay, or is there a better way to circumvent that problem?
Rather than using System Events to generate keystrokes, consider using TextEdit itself to insert text.

tell application "TextEdit"
    activate
    tell first document to set its text to its text &amp; "Hello World!\n"
end tell


There is a difference, though: this version always appends "Hello World!" to the end of the document, rather than wherever the cursor happens to be.  (Unfortunately, TextEdit's AppleScript dictionary mentions nothing about cursors.)

A side benefit of this approach is that you don't have to grant permission to use Assistive Access to your script.