Hi Reticent
I make ambient music,(although mine is dark and sinister and downright creepy,roll on Halloween 2013) Ha,ha!!
But I'm also in the process of working on lighter stuff at the moment,for my next collection
But the principles are more or less the same,as follows.
Experimentation is the key! I use Live 8 suite with Reason 6.5 via rewire.Sometime Live on its on,depends on how complicated I go with the track
The basic rules I follow are:
1) Sound design (experimentation)
2) Recording
3) Sequencing and arrangement
3) Mixing
4) Mastering
I have stuck to these principles,and they work for me,with a doubt!! Ha,ha
Have a look on Soundcloud,there are a lot of ambient people on there (me included,lol)
Also Youtube, and Wikipedia,plus of course films,dvds etc,as well,to give you a good understanding and/or inspiration
Sound- wise,usually pads,reverbs,good percussion,beats,effects,etc,etc all play a part .As well as vocals sometimes,and outdoor sounds ie running water etc,a huge choice to be had out there!
I also thrash out ideas onto a small white board,(the kind found in colleges etc), first,and that gets me going on ideas.
just have fun,and experiment don't rush in.I been with Live only recently (last year) and with Reason for 4 years and still learning
Also remember to have frequent breaks, and make copies of your tracks ( this way,you could have several versions,before deciding on the final one)
A good idea is to use an external hard drive.They are quite reasonable to buy these days,put your work on that,or have a copy of it in there
,Back ups are essential!
As you can tell,from my response to your posting, I'm passionate about ambient,stuff lol

.Please feel free to pop by my Soundcloud page and check out my work ,give you an idea or two,lol)
Any questions or help,Pm me there or here,and I shall see if I can help you out further,ok
All the best in your new adventure!!!!
http://soundcloud.com/ambientdave