To answer your first question (if you intended for it to be answered), attendance means the act of attending something, or being present (at a meeting or event), and experience is the knowledge or skills you gain from participating in or being present at a certain event. When it is a verb, experience signifies having a first-hand experience of (a feeling/thought/circumstance) [ie. I experienced severe nausea on the flight home]. Please excuse the extremely brief and incomplete definitions of these two words.
As the for second part of your question, there is sort of a rule when it comes to '-ance' and '-ence' nouns.
Semantically, ‘-ance’ and ‘-ence’ basically signify the same concept – they are just spelt differently. A word that ends in ‘-ance’ is often a nominalised form of an adjective that ends in ‘-ant.’ (ie. observant/observance, compliant/compliance, distant/distance). It can also also be the nominalised form of a verb (ie. assure/assurance, admit/admittance, resemble/resemblance, purvey/purveyance).
Nouns that end in ‘-ence’ can usually be coupled with an adjective that ends in ‘-ent’ (ie. reverent/reverence, different/difference, ambient, ambience). Some may be the noun forms of verbs (ie. offend/offence, abstain/abstinence, depend/dependence), or they may be able to act as both a noun and a verb all in the one word (ie. experience, licence).
Some adjectives that end in ‘-ant’ or ‘-ent’ have a noun form that ends in ‘-ancy’ or ‘ency’ (ie. pregnant/pregnancy, regent/regency). You may even come across an adjective that has both a ‘-nce’ and a ‘-ncy’ ending (ie. adamant/adamance/adamancy). Remember, there are also some nouns ending in ‘-nce’ that do not fit into any of the categories above (but, I can confidently say that most of them DO).
Due to the complexity of English and the languages it derives from, it can be really tricky to guess the noun forms of verbs and adjectives. The only tip I can give you is to learn an adjective or verb with its noun counterpart at the same time (or vice-versa). Online dictionaries usually have the related forms of a word listed in the same entry as the word. This way, you will probably have better luck remembering the right spelling. Good luck! (and sorry for the long response) -Joel