I'll use one of my teams as an example...C11 Lima Alchemist. I picked the team up as an unowned team years ago. I struggled with losing records for years. I drafted rookies and slowly accummulated the pieces of a championship organization. The team came together, and now challenges annually for the playoffs. I have alternated first and second with a tough Jersey team for the last 5 years. My team has won the division the last two years, the league championship the last two years, but lost both times in the world series. The team is set to contend in the future too. My team is usually winning most years...not the bipolar first to last to first like some teams.
Here's how I got the key team players...

Rookie drafts:
Helton, Hafner, Jeter, Manny Ramirez (2nd round rookie pick!!), Floyd, Benitez, Valverde, Baez, Sabathia, Oswalt (traded Carlos Delgado to get the first round rookie pick to take Oswalt).

Trades: Brian Anderson

Free agent Picks:
Aramis Ramirez (someone had cut him prior to the free agent draft...and I used my FA1 to take him even though it took about 2 years before he finally took off and got good), Vernon Wells, Posada, Stairs, D.May, Madson (last year), Duchscherer.

Original team member: B.Boone, Ausmus

Note: Free agent picks are key to development also. I always look for top prospects that get a Sept. call-up, do poorly, get drafted as rookies, do poorly in limited use the following season, and get cut by teams in the "cut to 27," and are available in the first round of the free agent draft of their 2nd or 3rd year of big league play. They are still not useful for my team...but I grab them (like V.Wells, Ar. Ramirez) because they will probably become stars, and I use them to sit on my farm for another season or two until they are ready to play regularly.
I have had to cut prospects in the "cut to 27" too, and have often wished I had held onto the prospect, and cut the veteran OF instead. But sometimes I also get short-sighted about what I can use next season, vs. the longer view of 2-3 years down the road.
I also try to plan ahead...I have B.Boone at 2B, and he may be nearing the end of his career soon...so I start looking for a prospect 2B to take over in a few years.

So, the good teams are consistently good due to good planning.
I don't like the managerless trades much, as I think the Manager-less teams lose solid veterans, even stars, for rookie picks (which may never become the equal of the stars traded for the picks).