-do i recite the phrases out loud or just in my head?
It's best to engage all the senses that you can. So during day - say them out loud (to think and to hear them) when you can, or just whisper, or just think them in your head. As you going to sleep, start with saying out loud, and as you getting more sleepy, switch to whisper and then just think them.

-what are some good phrases to tell myself as i fall asleep?
Anything that feels right and makes sense for you. Mantras can be used for all different purposes.
"I wake up at x time" - to wake up at certain time instead of using alarm clock
"I wake up after each dream and remember it" - to write down your dreams at night
"I remember my dreams"
"This is a dream"
"I'm dreaming"
and many more

-does it make a difference between which tense i say the phrases in? example: present tense: i lucid dream tonight. future tense: i will lucid dream tonight.
Mantras should be in present tense. Our mind knows only 'now' and "not now", meaning any time in the future.
you want the stuff to happen now, not next week or month or year.

Here is more about mantras Collection....DILD
Mantras tutorial
Happy dreams