Experience & Advancement

Experience Points
So, how does my heartbreaker handle experience points? Here's the basics:

1 XP for every silver penny worth of treasure recovered by or awarded for adventuring
1 XP for every silver penny frittered away on tithes, carousing, ostentation, training, etc.
100 XP per HD of foes slain or otherwise overcome, up to several times that for monsters with especially dangerous special abilities (note that this is a comparatively minor source of XP). 

Given that HH uses the silver penny as the base unit of currency (more on that later), the first and last entries are bog-standard, whereas the second is an extra kicker that has much in common with various rules for drinking and wenching from the hobby's elder days. XP is conventionally awarded when treasure is divided, but that doesn't necessarily grant a new level right away. I don’t mind the double-counting of treasure, that just means its okay to give out less without retarding progress and that players face an interesting choice between getting more XP and making useful purchases for adventuring.

Gaining Rank

First off, characters in HH don't have levels, they have Ranks. Level is a word much over-used in D&D, so in HH it is solely relegated to describing sections of a dungeon. Similarly, spells come in grades of Complexity instead of level.

Anyway, after accumulating the necessary experience points, characters require 1 week of downtime in a relatively safe location in order to progress to the next Rank. At this time the character’s Hit Dice increase, directly improving the character’s fighting ability, hit points, and Saving Throws. All Hit Dice are re-rolled at each level, but hit points never decrease as a result (keep the old value if it is higher). Spell-casting characters also immediately gain the ability to cast more and higher-complexity spells.

Earning Titles

Part of character advancement is the renown and social status that comes with the character’s growing wealth and ability. While class ranks are not a part of the world as recognized by characters in-game, class titles are, and society in general or the character’s superiors will come to give the character new recognition as each new tier of ability is reached or shortly thereafter, often with some ceremony or other official mark, unless the character is unusually unknown or infamous. Titles are specified for Ranks 0, 1, 3, 6, 9, and 12, which are also tied to various class ability graduations.

Training and Education

Characters will have to seek out opportunities for training and research in order to learn new spells and Warrior disciplines, which may be done during the week of downtime needed to level up at the referee’s option. Characters may also attempt to learn new trades, spells, or languages at any time; this simply requires time and the availability of a tutor or other leaning materials. (Note that I use a variant of the rule from Lamentations of the Flame Princess that allows characters to know a language with a die roll, instead of having to pick them from the beginning).