Old-school photo. (Steve Marcus for The Washington Post)

If your idea of NCAA tournament gambling goes beyond simply filling out your bracket, this preview is for you. Here are some things to consider before you make your against-the-spread selections.

Seed trends

Here are some opening-round trends to consider, via ESPN’s Mackenzie Kraemer. Keep in mind that these are hardly predictive and that basing your picks solely on trends is far from advisable. Instead, add them to your overall knowledge base. All point spreads referenced below were taken Tuesday morning from the consensus lines at VegasInsider.com:

No. 1 vs. No. 16: Top-seeded teams are 6-10 against the spread (ATS) in the first round over the past four tournaments. But since 1985, No. 1 seeds are 14-5 ATS in the opening round when the line is 19.5 points or lower, including 7-1 over the past 10 seasons. The two No. 1 seeds who know their opponent already — Gonzaga and North Carolina — are favored by more than 19.5 points.

No. 2 vs. No. 15: It’s an 18-18 ATS split since 2008, but over that span, No. 15 seeds that get at least 18 points are on a 7-1 ATS winning streak. Troy (+19), Northern Kentucky (+20) and Jacksonville State (+20) all fit the bill this year.

No. 3 vs. No. 14: Over the past three seasons, No. 14 seeds that get at least 12 points are 6-2 ATS in the first round. As of Tuesday morning, this applies to all four No. 14 seeds: Iona (+14.5), Kent State (+17.5), Florida Gulf Coast (+12) and New Mexico State (+12.5).

No. 4 vs. No. 13: From 1990 to 2013, favorites in this matchup were 54-41-1 ATS. But since then, they’ve gone just 5-7 ATS. Since 2012, No. 4 seeds that were less than a 7.5-point favorite have gone 2-5-1 ATS with three straight-up losses. All four No. 4 seeds this year are at least 7.5-point favorites, though Purdue (-8.5) is close against Vermont.

No. 5 vs. No. 12: Favored No. 5 seeds have gone just 11-21 ATS in the first round since 2009.

No. 6 vs. No. 11: Since 2009, No. 11 seeds are 19-13 ATS against No. 6 seeds. Plus, the last five times a No. 11 seed was favored over a No. 6 seed, it has gone 4-1 ATS. All of the No. 6 seeds who know their opponents this year are favored, though the line could swing in the Creighton-Rhode Island matchup (the Bluejays are one-point favorites as of this writing).

No. 7 vs. No. 10: No. 7 seeds that were favored have gone 7-4 ATS in the first round since 2013. Only one No. 10 seed — Wichita State (-6) vs. Dayton — is favored this year.

No. 8 vs. No. 9: Underdogs have gone 20-9-3 ATS in this matchup since 2009, and when the line is within three points, the underdog has covered the spread in 10 straight games. Miami (-2) vs. Michigan State, Arkansas (-1) vs. Seton Hall and Vanderbilt (-1) vs. Northwestern all fall under that category this year.

Beware the trendy underdog

It’s a mantra that applies to all sports, but it’s an especially wise rule of thumb in March: Think long and hard about backing an underdog that’s getting a lot of attention from the betting public.

As noted by David Solar of Sports Insights, NCAA tournament underdogs that get more than 50 percent of the spread action have gone just 82-105 ATS since 2005. And if those trendy underdogs are getting less than 10 points while receiving a majority of the spread bets, they’ve gone just 68-95 ATS.

Here are some of the more heavily bet underdogs as of Tuesday morning (Sports Insights offers bet percentages here). The bolded underdogs are getting single digits and thus perhaps should get even extra scrutiny: Virginia Tech (+5.5), Bucknell (+14), UNC Wilmington (+7.5), East Tennessee State (+10), Florida Gulf Coast (+12), Winthrop (+11), Marquette (+1.5), Seton Hall (+1), New Mexico State (+12.5) and Rhode Island (+1).

In the first and second round of the NCAA tournament, favorites getting less than 50 percent of the spread bets have gone 73-51 ATS since 2005.

Boring down into the matchups, unpopular No. 4 seeds have been good plays of late. Those fourth-seeded teams that have received less than 50 percent of the betting action gone 8-1 ATS since 2005. So perhaps pay particular attention to Florida, Butler and West Virginia: All three of those fourth-seeded teams were getting less than 50 percent of the action as of Tuesday morning.

Good/bad against the spread

Best/worst coaches

Via Sports Insights, here are the coaches with the best and worst NCAA tournament spread records since 2005.

Best

1. John Beilein, Michigan: 14-5. Beilein is 9-1 ATS as an NCAA tournament favorite since 2005, and the Wolverines are small favorites against Oklahoma State as of this writing.

2. Sean Miller, Arizona: 16-9. He’s only 8-8 ATS as coach of the Wildcats, though.

3. Chris Mack, Xavier: 9-3.

4. John Calipari, Kentucky: 25-19.

5. Gregg Marshall, Wichita State: 11-6.

Worst

1. Mike Brey, Notre Dame: 5-11 ATS. Though, oddly enough, Brey scored a win and a cover against Beilein in last year’s first round.

2. Mark Few, Gonzaga: 11-14 ATS.

t-3. Greg McDermott, Creighton: 2-5 ATS.

t-3. Leonard Hamilton, Florida State: 2-5 ATS.

5. Tim Cluess, Iona: 0-3 ATS.