Concerning lipliner that it is not obvious, I had written:
Another solution is to line the lips using a lip brush with the color you intend to apply: this is especially useful for applying highly pigmented matte lipsticks. [This advice originally came from Bobbi Brown]
ArtDeco, a cosmetics company from Germany, offers a Color & Contour Lip Duo, which features lipstick at one end and contour at the other end for lining the tips. This is a highly pigmented lip color, so blending is still necessary.
Now I think that both techniques result in an overly obvious line, which is why I now prefer clear lipliners or lipliners that perfectly match the color of one's lips (which is why MAC's Lip Pencil in Spice has been so popular).
I've since discovered that companies other than Revlon and Paula's Choice offer clear lipliners, but at a higher price: DuWop Reverse Lip Liner and CARGO The Reverse Lipliner.
Lastly, the March issue of InStyle featured an excerpt from Bobbi Brown's latest book Living Beauty. Bobbi Brown wrote that the most flattering lip color is two shades darker than the natural color of your lips. I can vouch for her advice, after a lot of experimentation (and a lot of money spent!). One also has to take her complexion, hair color, and clothes in account when selecting lip color.
I'm light to medium in complexion, with dark brown hair and brown eyes. While I had been classified as a "Winter" (using the seasonal color typing that was so popular in the 80s), I tend to favor rich warm colors over cool colors. Some of my favorite lipsticks are Bourbon from last year's limited edition Catherine Deneuve color collection from MAC and Bésame's Enchanting Lipstick in Chocolate Kiss, particularly when wearing brown. In fact, I favor lip colors that are "ambiguous," that is, not too cool, not too warm.
Another tip is to apply lip color just slightly inside your mouth (I would name the source of this tip if I could recall it) so that there won't be any apparent demarcation lines; also, this application suggests fuller lips.