I think it depends on particle, but basically it points out the role of the word it follows. For example: "を"- たまごを食べます。I am eating eggs. "を" points out たまご as the object of eating. (If that makes any sense). "が" - たまごが好きです。I like eggs. "が" labels たまご as the subject of like "好き"・ "か" - これはたまごですか？ This is an egg. "か" makes the sentence as a question. I hope my explanation was not too confusing.

It all depends on which particle you will use, but mainly after the content word, meaning the word that carries meaning rather than grammatical functions like particles. For example, Sentence: Watashi WA(particle) kaimono E(particle) Ikimasu. Meaning: I (noun) shopping (noun) go (verb, present tense - masu form (polite)) Translation: I go shopping. The very basic usage will be like above. It might be easier to think "particles" as a glue of words. Though in casual conversation, the particles as such are often omitted, but instead the particles that carry meaning or connotation will be used more. For example: Sentence: Kyo, shiken da-NE(particle). Meaning: today exam be (present, casual)-PARTICLE (function: affirmation, asking for response, responding to the other.) Translation: It's exam today, eh?/huh? (eh? is Canadian usage, sorry.) Probably I gave you too much information. But one thing in common: it comes after content words. There is "Dictionary of Japanese Particles" (http://www.amazon.com/Dictionary-Japanese-Particles-Sue-Kawashima/dp/156836542X). You might find this useful.