If I understood you correctly, strings are definned in an STR file. What you do is open up Notepad & type:

NAMEOFSTRING
"STRINGTEXT"
End

So bassically, in the briefing action of a script, type a name of the string, like, Caption 1. Then if you wanted the caption to say, "Welcome to my map!" Then the text in Notepad should look like this:

Caption 1
"Welcome to my map!"
End

Now all you have to do is save the Notepad file as "Map.str" in your map folder. (The folder for youre map in located in "My Documents\Command & Conquer Generals Zero Hour Data\Maps" [Assuming your using Zero Hour & not Generals.])

If you are using Zero Hour & not just Generals, then take note, if you're doing this for a multiplayer map you'll see on your screen, "Welcome to my map!" while the other players will see, "MISSING: 'Caption 1'". (In just Generals there's no problem. This only accours in Zero Hour.) There's no way around this, unless all the players have the map in advance, so just use the caption as the string name. So in the briefing action of your script, put, "Welcome to my map!" Then in the Notepad file, change the text to:

Welcome to my map!
"Welcome to my map!"
End

Then at least the players will see, "MISSING: 'Welcome to my map!'". After they player exit Zero Hour & open it up again & play the map again, then the caption will come out right, without the MISSING infront of it.

What else can I do?

What do you mean?