Reese Witherspoon and Owen Wilson play a pair of on-again-off-again lovers in the romantic comedy How Do You Know. (David James/Sony Pictures)

Early on in James L. Brooks' romantic comedy How Do You Know, the film's type-A heroine, Lisa (Reese Witherspoon), winds up in bed with Matty (Owen Wilson), a dim pro-baseball player whose knack for wooing women is nearly as impressive as his fastball.

At a time when a lot of romantic comedies are populated by needy twits, it's refreshing to see a genuinely smart female character.

When the glowing, post-coital Lisa discovers Matty's bathroom is stocked with pink tracksuits and spare toothbrushes — gifts the gracious host prides himself on offering his conquests the morning after — she senses this playa isn't boyfriend material. But she sticks around, anyway. Who can resist the promise of some good times, when finding a deeper love seems all but impossible?

Lisa's attitude provides a handy approach to How Do You Know, a curious, slow-burning rom-com where the rewards come in fits and spurts. As a whole, it's a bit of a mess, but if you hang in there, the movie manages to generate enough easygoing charm and laughs to make you glad you stayed.

Like James L. Brooks' beloved and far superior Broadcast News, How Do You Know focuses on a trio of highly functioning professionals who don't have the first clue about relationships. At the centre is Lisa, a successful softball player for a national team, who's about to be put out to pasture at the ripe old age of 31. Early retirement is clearly not on this perfectionist's agenda: standing alone in her bathroom (surrounded by Post-It note affirmations like "Stupidity should be painful!"), Lisa takes the news hard, brushing her teeth vigorously while wiping away big, blobby tears.

Across town, nice guy George (Paul Rudd) is also hitting a career low, having been informed he's being investigated for securities fraud. It's a murky corporate crime that's never properly explained, but one that likely involves George's weaselly father and boss, Charles (Jack Nicholson), a selfish monster prone to shouting lines like "Cynicism is sanity!"

Reeling at the prospect of starting a new life, Lisa ups her late-night booty calls to Matty's condo, but also manages — thanks to coincidences that exist only in romantic comedies — to wind up on a very awkward lunch date with George. The two make an impression on each other, and eventually forge the beginnings of a clumsy but mutually nurturing friendship. All the put-upon George knows is he feels better around Lisa, while he introduces her to the foreign concept of talking about her emotions.

In the midst of this life crisis, Lisa begins to see a shrink (Tony Shalhoub), who urges her to "figure out what you want, and learn how to ask for it." This succinct advice winds up being the thematic force behind How Do You Know, as all of the characters take fumbling stabs at finding what will make them truly happy.

Shalhoub's directive proves easier said than done — indeed, Matty's brain cramps whenever he tries to contemplate something beyond a one-night stand. The movie struggles, too. In the film's meandering first hour, Brooks is so committed to studying each of his characters in their own orbits, you might find yourself wondering when the film's going to achieve some momentum.

When he focuses, though, Brooks still has a gift for broad, smart comedy. An early bit involving George's attempts to drown his sorrows in steak, Teddy Pendergrass tunes and a ridiculous amount of booze is played with such flair by Rudd that it'll tide you over until the film's second half. And there's a scene later in How Do You Know that is such a marvel, it makes the lengthy buildup worthwhile. As two characters play out a hospital-room dialogue that looks to be as cornball as you'd expect, Brooks pulls a sly bait-and-switch that manages to undercut, even comment on, the sappiness, while still keeping you hoping for a sentimental outcome. This is inspired writing — truly as good as it gets.

Brooks' players handle this material like seasoned pros — they keep things bobbing along, even when the film's structure threatens to fall apart. Rudd easily bests Nicholson in a duel to see who gives the best reaction shots, and Wilson is just as endearing, investing all of his scenes with puppy-dog energy that's tough to resist. Some of How Do You Know's best moments come courtesy of Matty, especially when, in hapless-boyfriend mode, he begs Lisa, "Can I just finish my thought, please? Maybe it'll help, maybe it won't, but I'm trying."

In the end, however, it's Witherspoon's movie. The actress is always winning, even if she fares better in self-assured scenes than in the moments when she has to dither. As her character inches toward some kind of self-awareness, you'll be reminded of how many complex women Brooks has written in his career, from his Mary Tyler Moore Show days to the feisty mother-and-daughter duo in Terms of Endearment.

Lisa isn't quite on par with those formidable dames, but at a time when a lot of romantic comedies are populated by needy twits, it's refreshing to see a genuinely smart female character — one who cares about her career and worries aloud that she might not make a great wife or mother. Lisa might be lost, but Witherspoon always makes her feel real. I found myself invested in her outcome, giddy towards the end that both Lisa and the movie had finally figured out where they were going.

How Do You Know opens Dec. 17.

Lee Ferguson writes about the arts for CBC News.