I'm not sure that I have a hard-and-fast definition of successful. I can point to some successful coaches, and I'd like to be as good as them someday, but I just tend to take goals one at a time. Here's about how my goals have progressed for D2/D3 (D1 is an entirely different animal, and I've never even made the PIT there, albeit in only five seasons across two worlds). Starting with the "new coach" goal and moving on to higher ones.
1. Build a team that makes the NT consistently (75% of the time or better). Accomplished. I read the forums voraciously when I joined HD, so this one really wasn't too hard for me. Almost all of my teams make the NT year in and year out. My first HD team made it in season three and has not missed since. Overall, I have a 71% NT rate at D2/D3, but I've also taken on a number of total rebuilds. If you take out the first two years of all of those rebuilds, the NT rate jumps to around 90%.
2. Build a team that can win games in the NT, while continuing to do (1). Accomplished. This one was tougher. I lost in the first round of my first three NT appearances with my first team and was losing in the first round with each successive team I got. Adjusting recruiting standards from "build an NT team" to "build a threatening NT team" was difficult and important. I had to learn which players could fill roles on great teams and when you were better off taking a walk-on. It took me until season six with my first team to finally break into round two. Overall, I now make the 2nd round about 55% of the time, and if you adjust for rebuilds, it's about 70%.
3. Build a Final Four team, while consistently doing (2). Accomplished. This might seem like quite a jump from goal #2, but my first four teams to break through the first round all made the Sweet Sixteen, and three made the Elite Eight. The change in recruiting standards made a big difference, and so the next goal was a big step from the last goal. I didn't make my first Final Four until playing HD for a full year, and I'm not sure it was about making big changes from the previous teams so much as just building good teams consistently enough that eventually one got lucky.
4. Win it all. Accomplished. The move from (3) to (4) didn't take long. My first Final Four team won it all. Honestly, I am not inclined to view doing something once as a good definition of success, but getting rid of that "0" next to "Championships:" felt like a huge accomplishment, and it'd be disingenuous to say it wasn't a goal.
5. Build Final Four teams/legitimately compete for titles in multiple worlds. Accomplished. Doing it once is one thing, especially if you have a team in a really nice recruiting area. Doing it with different teams is tough. It's about finding that consistency in a variety of different circumstances, not necessarily the most favorable. Apart from one odd run to the Final Four as a 9-seed with Alaska-Anchorage, it took a long time to make my first Final Four outside Crum. Almost a full year after my first Final Four inside Crum. Now have Final Fours in four worlds and championships in two worlds, but it took a lot of doing.
6. Consistently compete for titles with all D2/D3 teams. Still working. Not necessarily requiring a title contender every season in every world, which is unrealistic even for the all-time great HD coaches, but often enough to be one of the regulars (perhaps Elite Eight 40% of the time, Final Four 15%? Not as an average across all worlds, but actually getting to those benchmarks in each D2/D3 world I'm in). I am definitely one of the regulars in some worlds. In Crum I've made the Elite Eight in nine of the last ten seasons and the title game in four of the last eight. But across all my D2/D3 teams, even if you adjust for rebuilds, I only have about a 30% rate of making the Elite Eight and 10% of making the Final Four. I have one D3 team that still hasn't made a Sweet Sixteen after six seasons and still have five D2/D3 teams (out of seven active ones) that are looking for their first Final Four. Never won a D2 title, and none of the teams I thought were title contenders have even made the Final Four. Still plenty of work to be done on this count.
So that was a lot of me talking about myself (sorry), but I think it provides a nice illustration of how to structure your goals depending on where you are in your HD life. Start with making the NT consistently, and then every time you accomplish something, set a higher goal. Right now, I've made it through five of my personal goals and are working on a sixth, but there are HD coaches who can blow my goal #6 out of the water and are on to something bigger and better. But for now, shooting for all-time great level is unrealistic and discouraging. I just want to be a regular contender wherever I coach.