Before Charlotte Tilbury had a brand, she was a makeup artist mixing lip colors by hand backstage, chasing a nude-pink that flattered almost everyone. In 2013 she finally bottled it, or rather sharpened it, as a lip liner called Lip Cheat in the shade Pillow Talk. It was a pencil, not a lipstick, and it became the most famous shade in her line, later turned into lipstick, eyeshadow and blush.

I love that one of the biggest makeup stories of the last decade started with a liner, because it says something true about the product. A good lip liner does far more than stop lipstick from bleeding. Drawn along the natural edge, smudged in and topped with balm, it is most of a lip look on its own. It evens out a lopsided cupid's bow, makes a sheer gloss look deliberate and keeps color in place through a meal.

The real choice when you buy one is whether you want it to stay or to blend. Long-wear and waterproof pencils are firm, precise and made to survive dinner. Creamy ones are softer, move with a fingertip and feel closer to a balm. Both are useful, and most people I know end up owning one of each.

Here is a test I like: swatch the pencil on the pad of your fingertip, not the back of your hand, and hold it next to your mouth in a mirror. Fingertips are closer to lip color, so you will see which shade disappears into your lips.

These are the all day pencils, the ones to use when you are going from a morning meeting to a late dinner without a mirror in between. Here is the method that makes them last: line the edge, then fill in the whole lip with the same pencil before any lipstick or gloss goes on. The liner becomes a base coat, and when the top layer wears off, what is left is still color, not a ring.

Charlotte Tilbury's Lip Cheat is velvety, waterproof and transfer-proof and lasts up to six hours without feathering. Urban Decay's 24/7 Glide-On is the marathon runner, creamy but waterproof, with up to 16 hours of wear and 25 shades. Fenty Beauty's Trace'd Out is made with pure pigments so every lip tone gets true color without looking ashy, which is harder to find than it should be.

Make Up For Ever's Artist Color Pencil is a longtime bestseller, creamy and soft-matte with a precise tip, now in shimmery finishes too. Huda Beauty's Lip Contour 2.0 is a retractable matte pencil, so there is no sharpener to lose. ONE/SIZE's Lip Snatcher is intensely pigmented and waterproof, softened with cottonseed and olive oils. Sephora Collection's Colorful 8HR is a transfer-proof matte that stays comfortable, and YSL's Kiss Shaper is creamy and transfer-resistant, with jojoba and coffee oil.

What I would skip: long-wear liner on dry, flaky lips. Balm first, blot, then line, or the pencil will catch on every rough edge.

This is the group I reach for on weekends, when the whole point is to look like you did not try very hard. These pencils are softer and more hydrating, and they are meant to be smudged. Line, then press a fingertip along the edge so it looks blurred into your lip rather than drawn on. Add a clear balm on top and you are done.

Makeup by Mario's Ultra Suede is the bridge between the two grids: a matte, full-coverage pencil with a blending brush on the other end, and an Allure Best of Beauty winner. Kosas's Hotliner is retractable and made with hyaluronic acid, so it softly contours without drying. Summer Fridays' SoftLine blends easily and uses hyaluronic filling spheres with coconut and jojoba oils to keep lips comfortable.

Saie's Lip Liner 101 is a classic wooden pencil and nearly foolproof, with meadowfoam oil and shea butter. Glossier's Lip Line is creamy and sharpenable, with a grip complex that helps it stay. Merit's Signature Lip is the sheerest here, a liner you can also scribble over the whole mouth for a wash of color. Westman Atelier's Lip Shape comes in true-to-life shades and glides without tugging, and REFY's Lip Blur is a soft-matte pencil made to blur the edge and make lips look fuller.

Here is a pairing I like: Merit's sheer liner all over, with a dot of gloss in the center of the lower lip. It looks like your lips, only better rested.

What I would skip: a sharp, dark creamy line with nothing over it. Blur it, or it reads as a drawn-on edge.

I think lip liner is the most underrated thing in a makeup bag, and the easiest to get right. If you only buy one, pick a shade a touch deeper than your natural lip, in whichever formula suits your week. It will work under nearly every lipstick you own, and on its own it just looks like good lips.

Wear it for a week before you judge it. Liner is a habit more than a product, and once you are used to that bit of definition, a bare mouth starts to look a little unfinished.