...I'm stuck on a couple points:
1. How do you make a mechwarrior campaign interesting? I mean how do you add more than mech battles in a compelling manner?
A few words on this.
1) Know your group. The main thrust of almost any game is to have a good time. If this is a group you know well and have good chemistry with, then all you're really doing with the switch to Battletech is changing up some names, faces, and places.
Admittedly, it helps to know the universe well, or you might struggle a bit to come up with a compelling storyline that's plausible in a BT setting (though, if the rest of the group is clueless, you might be able to sneak your ignorance past them ;) ).
2) Know how to tell a good story. I think that's a pretty common rule for any game master in any universe.
3) Remember that battlemechs are driven by people. People are, often, more interesting than battlemechs.
Mechwarriors weren't born in their mechs (though Clanners may come close ;) ), and they don't live in their mechs (unless they're those addicted protomech pilots who won't even exist for another decade or so, in game time).
If you're playing Clan characters (which seems to be the case), your best bet is to learn as much about their society as possible. The warrior caste is an arrogant, honour-bound lot driven by pride and a need to excel above everyone. If your group consists of mixed-caste characters (some warriors, some merchants, scientists, techs, or labourers), you're probably going to have some automatic tension in the form of the warriors' condescending attitudes toward "lower castemen."
Even in a pure warrior group, any warrior who was not born in a vat (a.k.a. "iron womb") will be given all the hatred due a "freebirth".
Even if your group is all of the same caste, and same relative social standing, well... people are people. Stuff happens.
Just play people as people. They'll have goals--frustrate them. They'll have dreams--crush them. They'll have aspirations--challenge them. If you were able to make past RPGs work without mechs, then fear not: A Time of War will be just fine for you. :)
I've been running my AToW campaign for several months, now, and we just barely had our first mech battle last session. It was almost incidental, but flowed very naturally from what the characters were doing (namely, taking their mechs and fleeing into the woods).
I think you'll do just fine. :)
2. This is going to sound kind of weird, but one of the players in my group only plays catgirls. She's played one in DnD, Shadowrun and basically everything else. I'm pretty lenient on the matter and figured with all that genetic tinkering Clan Nova Cat might try to mix in some of their totem animal's features as a little experiment.
But other than giving her the Good Hearing trait I'm not really sure how the mechanics would work out. Maybe Animal Antipathy since she has a weird scent now? Night vision? Bonus to Reflex?
I say, tell her to man up. Playing a normal person will put some hair on her chest!
Oh... wait...
Anyway, I think the advice already given is probably good enough. I don't know enough about the "Deeper" lore (heck, I didn't even know about the Canopian cat girls prior to reading this thread) to really add anything to it.
Honestly, just have some fun. I think if your friend is a one-off (I dig the experiment idea that was presented), that will both help with plausibility (since, honestly, how many cat girls
would be running around the Battletech universe; though, come to think of it, the Japanese influence of the Draconis Combine might pre-dispose many of their teenaged girls in that direction), and will make for an awful lot of good story hooks.
One other thing: if you're playing in the 3045-3050 era, well... when in that era are you playing? Are you starting in 3046 and then moving on into the clan invasion (3049 in the Periphery, etc.?) That might influence some things.
Additionally, the Clans prize conformity and pride themselves in their superior genetic engineering. How well they'd take to a "catgirl" character, though, I can't say. The Nova Cats, being the mystics they are, might be willing to run with the aforementioned "clan totem" idea. The other clans, though, might look at her as a total freak, and treat her with outright contempt (and maybe even hatred).
Any advice would be appreciated since I'm still learning the system myself (the life module system particularly)
Eh. It comes with time. I've learned that it's best not to get too hung up with the details if they're getting in the way. Of course, if you're still in the character creation stage, well... yeah. The details will matter a whole lot more.
If it makes you feel any better, I felt the need to build a spreadsheet to keep track of my character creation. I can e-mail it to you, if you want. Just PM me (and be aware that I don't check these forums all that frequently).