First let me inform you that even though these are ways to get a tier up. A staff can deny you for one at any time. For any reason. If you do not like a staff members ruling bring it to the owner and she'll see both sides of the story. However chances are high that if you got denied..it was for a good reason.
Tiering up via Re-evaluation of character app:
Basically in order to tier up this way you must ask a staff to re-evaluate your character's app. So say you've been with us for a few weeks and proven to be a good RP'er.. but started in tier 3 like all the others and don't want to tier up another way. You could ask staff to recheck it and retier it based on your RP's that you've done with us and ask if you could get a certain tier.
Tiering up via Challenge: When you think your character has fought enough times or hard enough people that he should become stronger. Ask a staff to get a fight together between your character and one of the tier you wish to be. Winning does not mean you will get the tier up. ( But it most certainly helps ) Two staff will monitor the fight and will not intervene even if god modding occurs until after the fight ( Though if the one fighting your character God-Mods during the match..he'll most likely lose a tier and/or Shuren ). If the staff judge that you followed the rules well. Gave alot of effort and detail. And proved you were worthy enough for that tier.. You'll get it. ( Most of the time you'll fight a staff member. but there will be times you'll fight another member. ) this is..in my opinion..the best way to get a tier up.
Tiering up via Character Development: Sometimes you got through a change in character and you think you should be stronger because of it. Such as training with the Captain Commander of Soul Society for instance.. or unlocking a new power such as bankai. When this happens just bring your case before staff and have them judge whether or not to give you a tier up. This is the least likely way to get a tier up but there are some cases where it could happen.
Tiering up via Shuren system:
You have to be the level directly underneath the level you wish to buy. So say you want your character to be 3-1, that character will have to be at 3-2 already. So for that same character to become 2-4 he/she/it will have to buy 3-1, 2-5 and THEN 2-4. Also, you can only tier up a character TWICE, then you'll have to wait another 50 posts before you can tier that character up again. Also, to get a 1-tier, you prove yourself via challenge. you cannot buy
4: Unbuyable (Since all will either be over or cannot be under this is unbuyable)
3rd Tier:
Tier Level 5: 200 Shuren
Tier Level 4: 300 Shuren
Tier Level 3: 400 Shuren
Tier Level 2: 500 Shuren
Tier Level 1: 600 Shuren
2nd Tier:
Tier Level 5: Unbuyable. You must challenge or be evaluated again to reach this point.
Tier Level 4: 1200 Shuren
Tier Level 3: 1300 Shuren
Tier Level 2: 1500 Shuren
Tier Level 1: 1800 Shuren
1st Tier:
Tier Level 5: Unbuyable as you must EARN this tier via challenge or re-evalutation first.
Tier Level 4: 4000 Shuren
Tier Level 3: 5800 Shuren
Tier Level 2: 6400 Shuren
Tier Level 1: Unbuyable - Challenge or re-evaluate to obtain.
O: Unbuyable (Reserved for Org. Leaders and Certain Event Characters)