You don't really need experience with livebearers, they breed quite successfully without much help.
If you really want to save some fry, then you can net them out when you see them & put them in another tank.
Feed a good quality crushed flake, or special fry food
I will go a bit more into detail with your question about the fry surviving
We need to know a few things before I can help you with how many will likely survive
whats the stocking, and how large are the fish
is the tank heavily planted
do you have something to prevent the fry from getting stuck in the filter
do you have lots of floating plants
how often do you feed your fish and how much
Yes, pregnant. A big black Gravid spot showing there.
Ideally they are best kept in a separate tank, if not, a floating breeding trap is another option. Just keep them separate from the adult fish that will eat them and feed them some fry food that will be available from your LFS. Or crush up some of your existing flake food for them.
If you set up a separate tank keep a close eye on the pollution levels.
Your biggest problem is netting them soon after birth as they won't survive long with the hungry adults about. As long as your do that, the rest is pretty easy. Best way to ensure they stay hidden from the adults after being born is to provide plenty of plants for them to hide in before you get a chance to net them. Bare in mind that most are born in the early hours of the morning, in darkness. So check on them as early as you can each morning, once you think the mum is about to drop them.
Yes, it's even more important then the adults to have the tank heated & filtered properly, but if they are in a breeding trap then it's not really a worry. If a separate tank, then the filter should be a low powered one and not capable of sucking the fry up into them.