How long should my script be before I cut? You should always create your piece from a source that is a little longer then you need. So if you are competing in HI, your script before cutting should be around 12min long. This way you have plenty of room to adjust without needing to cut significant information or stretch your script. It is always easier to make something shorter then to make it longer. Give yourself room to work.
Should I cut my script first, or write my intro first? You should always write the intro before you cut script. The intro is what pulls your piece together, so it is not where you sacrifice material to meet the time limit. You can definitely adjust it later, but make sure you cover everything you need to first and then cut the the piece to match. Instructions on writing an intro below.
How often do I need to practice? Every day? (As if that will really happen, but as often as you can.) It is best if you can practice frequently, even if it is in short bursts, rather then to only work on your piece a few times but for several hours. Better to review in short frequent settings then to cram.
A good place to look for Dramatic, Humorous, and Duo interpretation scripts is JD drama publishing and playscripts.com.
A good place to look for Prose is in memoirs and books of short stories.
https://www.youtube.com/watch?v=7ouDcXRU-rs
https://docs.google.com/presentation/d/1Oba6HpxAGP7cToD3vHleCRfyiWMbir_5XsmyzjN_nIU/edit?usp=sharing