So I've done quite a bit of research but my facts might be off a little (Since it's not coming straight from Riot) This is what I have found:
People with new ranks (Unranked never played ranked before):
Start at 1200 elo +/- 50 per win loss respectively
gain/lose elo depending on cs/champkills/assists (don't know this number)
People with previous ranks: Start at their elo for instance I believe I am at 1100 elo (which is actually higher than bronze 2) so you have a higher chance of getting into bronze 1 or silver.
+/- 50 per win loss respectively
gain/lose elo depending on cs/champkills/assists (don't know this number)
Bvigil you started off at 906 elo now depending on wins/losses and the amount you fed could be a factor in deciding your rank now (Bronze V is 800 elo)