After so many years of boss-hunting as my hobby I can say sad (at least for me) thing, that there are two major aspects that makes you a good bosshunter bosshunter with good results.
1) poulation on your server
2) your free time
... and now let me explain why.
First of all the most important is the server, on which you used to play. The more people playing on your server - the more boss-hunters. You should also add some people who sometimes have thoughts like "Oh, I'm so close to the respawn of Sir Valorcrest, maybe this time I'll be lucky!" and they check it without any wider knowledge about bosses. All of these players makes a competition. All of these players who check bosses may affect floor resets and floor resets may affect boss' apearance. Summary, the easiest way to meet a lot of bosses is to play on empty servers, where nobody, except you check it.
PS. I just checked the difference between amount of players on Antica - 750+ and Mitigera - 30+. As you can see, there is no comparison. If there is any boss-hunter on Mitigera - all bosses are his.
Second very important thing is your free time. Boss-hunting requires huge amount of time. Of course it depends a little bit on population on your server, but no matter if you have a big competition - you still need to check bosses quite often. If you want to have good results you can't make a boss-check twice per day. I know people who spend whole day on checking. They don't do anything else in Tibia, than boss-checking. No leveling, nor daily bosses. Sometimes they do boss-checks every 30-60 mins. In practice it means that they just end of their round and after 5 mins they have to start the next one. Souds horrible, but on the populated servers it is the only way to meet something, sometimes.
So now, when we're sure that we meet these two requirements, we can try to do our best:
1. We need to know the probability of boss' appearance. For example Dharalion can spawn between 6-8 day after his last spawn. You need to count it on your own or check it on TibiaBosses' predictions.
2. We need to do boss-checks as often as we can, but not too often to not affect floor reset. A lot of people make this mistake - they camp on the boss' respawn or check it every 15 minutes. Unfortunately it is more harmful than helpful. It may cause that boss will appear later, when often checks finally stopped and floor could reset. My suggestion is to not doing these kind of checks more often than 30 minutes. In case of more boss-hunters, even 30 minutes can be too often.
3. Be patient, be consistent. Sounds naive but I guess it is the most common reason why people give up with boss-hunting.
4. Also knowledge about tactics how to slain each boss is necessary. You want to kill Tyrn, not die by Tyrn because he drunk you so strongly that you get trapped. Right?
Here is a short guide how to start your checks, which might be helpful. It provide some more detailed info about easy bosses for low level characters: