How does a company get on the NASDAQ-100 index?

From Wikipedia, the index consists of the 100 "largest" companies (by market capitalization) that meet certain requirements.

The requirements for being eligible for the index are:

The NASDAQ has over the years put in place a series of stringent standards that companies must meet before being included in the index. Those standards include the following:

• Being listed exclusively on NASDAQ in either the Global Select or Global Market tiers.
• Being publicly offered on an established American market for three months.
• Having average daily volume of 200,000 shares.
• Being current in regards to quarterly and annual reports.
• Not being in bankruptcy proceedings.

and the calculation of "size" is market cap (share price * number of shares outstanding), using the following values:

There are two tools the NASDAQ uses to determine the market values of companies for the annual review:

• Share Prices as of the last trading day in October.
• Publicly announced share totals as of the last trading day of November.

Note that if a company falls out of the top 100, it does not necessarily get removed from the index immediately (see the Yearly rebalancing and re-ranking section)