Hi man, a good thing is to check great orchestral peices, like Beethoven's 9th symphone, and maybe Dvojak's "Symphony of the new world"...
You will notice immense string power in those ones. The trick there most of the time is octave doubling for a thicker sound, and also a lot of players play the same line, but with different instruments. Another important thing is mixing the orchestral sound pallete, like putting high woodwinds with low strings, you will see what i mean when you try to combine them in your music software.
Have great success!