I don't pretend to think it's easy, but there are certain mistakes an MLB GM makes time and time again, and it's not hard to avoid them.
First of all a disclaimer. You cannot count the Cashman, Epstein, and Hendry's in this. It's like sending my wife off on a shopping contest against Paris Hilton, Kelly Osborne, and J-Lo. Given all their means to come up with an outfit, perhaps one piece my wife might find at Kohls can resemble what they can find on Rodeo, but day after day, outfit after outfit, she will be outmatched.
But, she also doesn't need to just wander into Niemann Marcus and pay whatever to compete. Some tips (back to baseball).
1) Never ever overpay for a one to two year successful pitcher, particularly over the age of 28.
Examples: Randy Wolf (MIL), Woody Williams (HOU), Jeff Suppan (MIL), Chan Ho Park (TEX), Vincente Padilla (TEX), Carl Pavano (NYY). That just off the top of my head. How it worked out:
Wolf: Two seasons of 10+ wins in six years (only one of those over .500). Brewers sign him 3 years, $27.8M, another $1.5M to buyout 2013 at 33 or pay $10M.
Williams: At least 3 of last 4 years he had 10+ wins and winning record. But at 39, Astros give him $6M to go 8-15 with a 5.27.
Suppan: Only once in his career had an under 4.00 ERA, never gave up fewer hits than innings. Brewers at 32 pay him $40M over 4 years, shockingly ERA never goes under 4.00 and still never gives up fewer hits than IP.
Park: Okay 5 straight years of 13 or more wins, 11 or fewer losses, 4 with an ERA under 4.00. But it's in LA, not Arlington. Rangers pay $48M over 3 years at 29 to win 14 games and an ERA healthily over 5.00 all years.
Padilla: Two decent years over .500 with an ERA under 4.00 but it had been over 2 years when he won 16 games for Texas (ERA a pedestrian 4.50) and the Rangers re-sign him to $32M over 3 years at 29 (he did win 43 games)
Pavano: Two winning seasons ever (2000, 2004) most ERA's north of 5.00. Yanks sign him 4 years, $38M at 28.
2) The Japan market is tapped. Fukodome, Matsui (Hideki and Kazuo), Okajima, etc. all are never going to be Hideo Nomo nor Ichiro Suzuki. Yet we get year after year some GM (okay, mostly the above 3 free spenders) bring one in and spend a ton of money and get nothing. I'm not even bringing in Irabu.
3) Pay any player more than $15M per year at your own risk. Here's a hint, the chance for him to perform at a level to earn that is slim. In my estimation, there are about 4 players that will give you returns on that, their names are Pujols, Howard, A-Rod (slipping), and Morneau. Maybe Votto the way he's playing. Yet, you see a lot of Carlos Lee's, Jason Bay's, Carlos Beltran's, JD Drew's, Alfonso Soriano's, Derrek Lee's, and Kosuke Fukodome's. making that (ganging up on the Cubs there). Take the $18M, and get about 8 decent players (2 starters, 2 relievers, 4 end of bench guys) and see how it works out.
4) Draft well. I mean smartly. Balance college kids (fully developed physically) with high school kids (more of a wild card). It's not like Strasburg was a huge HS prospect, he developed, so don't tell me you can't find talent in college. Then there's the Purke (TCU) and Stubbs (Texas) who get drafted high out of HS but don't sign. Mix in some good HS talent and you'll do well.
5) Don't let signability sway your draft. I'm not saying pay what they want, but talent is talent and what's a few million dollars between friends. Don't sign the above pitchers and you can afford it.
6) Scout Latin America like crazy. Spend the money, find talent there, you don't have to draft it, and you can hit on about 10% and find a gold nugget.
7) Sign free agents that are <$5M and have an upside. Example Brett Myers this year. $3.1M this year, only 29. Never won fewer than 10 games with 30 starts. Same with position players. Find someone who can play 100 games and pitch hit for $3M.
8) Never overpay a closer. The other 24 guys have to get you in position to close and it's still random. Just rotate through guys who have good stuff, and when they demand more than $3M, make do with someone else. Someone like Rivera is an exception, again, with an unlimited budget you'd be stupid not to sign him. But the Angels and Rays and Braves have to find someone new every year.
9) Never be fooled by a postseason. Beltran 2004, Upton 2008, Mazeroski 1960, Hatcher 1990, prove that one postseason doth not make a star. It's as if one player had a hot 2 weeks (we've seen it from guys like Ty Wigginton and Juan Uribe midseason) and all of the sudden someone wants to throw $10M per at them.
10) Never overpay market value to re-sign resident talent. You have to let the Delmon Young, Adam Dunn, and Francisco Rodriguez's go. Trust me, you'll find yourself succeeding without them.
Follow those examples and I'm not promising post-season every year, but you'll put together a decent team every 3 or 4 years, then lose all your free agent talent to the Yankees and start over. But the White Sox and Cardinals have won as many World Series since 2000 as the Yankees and they just about never go out and just buy talent. Not to mention the Astros and Rockies and Rays have made World Series with minimal FA contribution.