The broadcast networks are making Friday nights a little more interesting this season.

Once home to some of TV’s biggest shows—think “Dallas” or ABC’s “TGIF” comedy hits—Friday has fallen out of favor at the networks in recent years. The night has become home to cheap reality fare, newsmagazines and shows the networks can’t bear to cancel.

There are signs that might be changing, although the fiscal realities of the night—lower ratings and less attractive advertising slots—mean networks still need to be creative in their approach to programming Fridays.

“It’s a night where usage is down,” said Preston Beckman, Fox’s executive VP of strategic planning. “Even if the show’s successful, you’re not going to get really big ratings on that night.”

And yet Fox and Mr. Beckman have just shaken things up on Friday.

The network has averaged a 1.6 rating among viewers 18-49 and increased viewership by 19% over last year with family-friendly reality shows (“Are You Smarter Than a 5th Grader?” and “Don’t Forget the Lyrics”). But last week it replaced those cheap-to-produce shows with two expensive hours that had originally been targeted for Monday: “Terminator: The Sarah Connor Chronicles” and new Joss Whedon series “Dollhouse.”

Mr. Beckman said Fox’s gambit is one born of need, not ambition.

“One of the reasons why we’re doing what we’re doing on Friday is we’re fortunate to have an embarrassment of riches,” he said. “We’re doing so well on all the other nights of the week that there’s really no room for these shows other than Friday. That’s a good problem to have.”

It’s too soon to say whether Fox’s strategy will work, but CBS has proven that risk can be rewarded on Friday.

CBS’ 8 p.m. and 10 p.m. dramas, “Ghost Whisperer” and “Numb3rs,” have drawn healthy audiences for several years now. And after stumbling with newcomer “The Ex List” in the fall, the network has found success at 9 p.m. with “Flashpoint,” a drama that had a successful summer run last year.

Overall, CBS has seen a 13% increase in total viewers and remained flat in viewers 18-49 this season, finishing first among all networks. CBS Primetime Senior Executive VP Kelly Kahl said the network’s consistency on the night has helped nurture its success.

“They’re shows that feel right for a Friday night,” Mr. Kahl said. “[They’re] successful shows, and people know where to find them.”

They’re also not breaking the bank, at least in the case of “Flashpoint.” That series costs CBS a fraction of what a typical one-hour drama costs, since it was originally produced for Canada’s CTV. That has allowed CBS to acquire episodes at a bargain rate.

Since moving to Friday, “Flashpoint” has averaged a 2.3/7 among adults 18-49 and 10.2 million viewers, outperforming “The Ex List” and last season’s “Moonlight.”

That’s good, because Mr. Kahl said CBS views Friday as “no less important” than any other night of the week.

“You really can’t expect the viewers to show up in droves,” he said. “You have to take the night seriously.”

Mr. Beckman, however, said Friday has not always been a priority for Fox.

“We generally schedule the other nights and then go, ‘What will we do here?’” he said of the night.

Nonetheless, Fox actually was doing OK on Fridays prior to its recent switch. Part of that improved performance is because of easy comparisons from last year.

“We’re up because we performed so poorly last year, not because we had a plan, to be honest,” Mr. Beckman said about the network’s average for the night. “In a perfect world, it’s about consistency. But I also think that given that usage levels on Friday night are lower than the other nights, other than Saturday, [and] given the cost of programming, you have to also be fiscally responsible on the night.”

Fiscal conservatism can be seen in ABC’s Friday night lineup.

This fall, the network dumped expensive dramas on Fridays and replaced them with reality series “Wife Swap” and “Supernanny,” while keeping “20/20” in its regular 10 p.m. slot. While the network lost some older viewers as a result, ABC has gained 6% among viewers 18-49.

ABC representatives were not available for comment.

Over at NBC, the network has made multiple changes to its Friday lineup after suffering big ratings losses this fall.

The network began the season with “Crusoe,” “Deal or No Deal” and “Life.” It then moved “Life” and “Crusoe” to other nights of the week and brought in the struggling “Lipstick Jungle.” The result: Season-to-date averages show NBC is down 31% among viewers and 32% in the 18-49 demographic on Friday.

While NBC would appear to be a loser on Friday, there is something of a silver lining in its ratings.

Like “Flashpoint,” “Crusoe” is an international production, one that costs NBC a relative pittance compared to a typical drama. So while it may have failed with viewers, its failure didn’t cost NBC nearly as much fiscal pain as, say, a show like “Ex List.”

NBC continues to use Friday for lower-cost fare this spring. Hidden-camera half-hour “Howie Do It,” which NBC is double-pumping to replace “Deal or No Deal,” is a Canadian co-production. And “Friday Night Lights,” now airing at 9 in place of “Lipstick,” is actually shared with DirecTV, which had the first run of the show’s season-three episodes last fall.

So far, the low-cost programming is producing mixed results.

The Howie Mandel-hosted “Howie Do It” debuted last month and boosted the network’s rating among adults 18-49 by 64% in the 8 p.m. hour. As of Feb. 8, “Howie” has averaged a 1.8 rating among viewers 18-49, leading NBC to order an additional 12 episodes of the series.

By contrast, “Lights” is averaging a 1.6 in the adults 18-49 demo, down from a 2.2. last winter, when NBC was the exclusive home of the show. The network will decide in the next few months whether the reduced production cost for the show is worth the reduction in ratings.

NBC representatives didn’t return calls seeking comment.

Not every network is in a quandary about what to do on Friday next season.

MyNetworkTV has already said it will keep its recently acquired “WWE Friday Night Smackdown” on the night next fall. And no wonder: The franchise is setting ratings records for the network, last month crossing the 4 million viewer threshold.