To start off, there isn't one single method of winning, there's quite a few standard methods, which people then fit to their own playing styles. So lots of different strategies there.
"1) I know you can transfer scientists & engineers the last few hours of the month to save on salaries...but can you
do the same with interceptors & skyrangers?"
A quick check in the game says yes.
"2) Given the short distances of the manufactured crafts, do any of you keep interceptors & skyrangers until you get Avengers? Or is the monthly rental too much (as long as you can't do #1 above)?"
My usual late game formation is 1 interceptor, 1 avenger and 1 skyranger (per base of course). Part of the reason is possible Elerium problems and part of it is that the avenger takes a long time to get repaired, wastes elerium and I don't really have the need for more than 14 soldiers, so I stick to the skyrangers.
"3) If you leave an area free of bases...does the game deter aliens from going there? I have the nagging suspicion that once you place a base in an area, the game starts more alien activity there. It doesn't make sense that you place 1 base in say America, but you then can't defend other areas since the aliens are hidden to you. Should we take our time in placing bases until you can stock one to defend an area, or does having early placements with little use but radar really help? Do the aliens attack other areas of the globe after a certain period of time? Because if not, then how do they expect you to defend the globe in the first few months?
4) Related to #3, how fast do you guys try to set new bases up?"
Well, I never used more than 6 bases, with a hyperwave decoder, I found them enough to cover the globe and provide a good network for fighter crafts. Meaning, I can more cover alien ships and prevent more of them from out flying my interceptors.
Again, there's many different things you can do with bases, from R&D bases, to listening posts, to full fledged bases. The reason you don't need to immediately cover everything is because the game starts off easier in the beginning You may have noticed that you encountered floaters or sectoids early on, but only later got to mutons and ethereals. Also, the aliens being easier will mean it will be easier to get a sufficient number of points to satisfy the funding nations. However, ultimately you want to prevent the funding nations from abandoning the project, because you can get a substantial amount of money. Of course, later on you'll mostly depend on selling off your equipment, but the money the funding nations provide you can be significant.
Personally I cover North America and Europe with the first two bases, then proceed with East Asia, and then with Africa, South America and Australia.
I set up new bases when I feel like I will be able to support it financially. In the last few games I've played, it ended up every 2nd-3rd month.
Personally, I don't tend to build listening posts, but if I did, I wouldn't do it until I felt like I'm out of the first months money problem. My secondary bases consist of mostly interceptors, some soldiers, a hyperwave decoder and sometimes labs and workshops. I do not build any kind of radar in a base until I have put some troops inside to defend it. Of course, if you're financially secure, then listening posts are a viable option, just be aware that they're at risk of getting destroyed also.
"5) I have heard that researching certain techs (like plasma) opens up the floor for harder aliens to show up. Is there any truth to this, and if so, are there certain techs to research last to avoid early difficulty?"
Not sure if it's tied to research, could be tied to how many months have passed. However, almost every piece of technology you get from the aliens is worth the more difficult aliens. Plasma weapons are really a class above most normal weapons you get. Not that you really have to use them all that much, laser rifles are quite good as well (always keep a few in the stores).
"6) I usually buy & sack soldiers until I get 12 decent 40+ bravery troops in the beginning of the game (I don't usually lose soldiers because I reload alot admittedly)...because I feel the faster I get 12 troops experienced, the better the game will be. I can then send 4 vet troops in the midgame to another area to help out once
I finally decide to get a tank. Is this a bad strat? I feel like using tanks early make 4 soldiers lose out on potential experience."
Well it seems like a waste of money, because early on, your soldiers are practically cannon fodder. Although it doesn't get a whole lot better with armors if you're playing on harder difficulties. Still, depends on your playing style, if you see it works, then you should use it. Ironman mode is a good way to asses how good your strategy/tactic is. If you lose a lot of soldiers every mission, then it's probably not good.
I immediately hire 12 soldiers. 14 of these go on missions, and 6 remain in case my base gets attacked while the skyranger is out. I used tanks a lot before, but now I just use them for base defense missions and Cydonia. I find 4 soldiers to be worth more, but for base defenses it doesn't hurt to have the tanks.
"7) Can someone give me a decent timeline on how many scientists and enginers you
should have in the opening months? I find the salaries to be a bit over the top, but the game designers couldn't intend for us to use the salary tranfer trick...how did they esxpect us to research in any decent amount of time with the costs of scientists?"
Again, more than one way of going about it. I get another 10 immediately and 5 engineers. Then when I get more living quarters, I try to get 50 scientists and 30-40 engineers. Doesn't happen immediately, but I always produce something - medikit when there's nothing important, because it sells well - so I like getting engineers as well.
"8) How many large radars do you use in your early bases? I try to get a sectoid navigator by the end of the first month to research for hyperwave decoder early. But I have read that people get better results with a large radar working in tandem with the HD (better distance?)."
1 larger + 1 small until I build the HD. Once I get it, I dismantle the other two, because they're not needed.
On another note, you can also find many answers on www.ufopaedia.org, and there's lots of thing you probably didn't know. Be sure to check it out.