Vocal clutter

I will be going into a studio for the first time in my life later this week to begin recording 10 tracks. I have one question. It might be answered somewhere on the site already, although I cannot find it.
How do I cope with phlegm? It knocks back my upper range, especially, for about 30 minutes, and is particularly noticeable in the morning during warm-ups.
It seems to be nothing terribly heavy. I’m not ill. I don't have a head cold. It’s just a lot of bubbly saliva (and I mean A LOT).
I know enough not to damage my voice by trying to cough it up, so:
1. How do I stop it happening?
2. What can I do to clear it faster, so I can get down to singing clearly?

Hello! I hope your studio time is a great experience and that the following helps:

- Increase hydration (around the clock, not just right before singing)

- Attempt to gently clear phlegm with lip trills or other gentle exercise

- Spit out phlegm if possible 

- Avoid foods/drinks that you find thicken or increase phlegm (sometimes dairy, sugar, and spicy foods)

- Allow ample time to wake up and warm up! 

- Warm up in the shower, inhaling steam

- Consider a nebulizer/vocal steamer (mypurmist, for example)

- Irrigate the sinuses with a saline sinus rinse

Good luck! 

Thank you, Camille. I am grateful that you took the time to reply. My first time in a pro studio was the most fun I have had in years. I go back next week to do pick-ups and harmonies. I'll certainly follow your advice.