First, if you're a Costco member you can use the coupon in your Costco coupon wallet to get a free $70-$90 account bonus. Create an account with the promotion code and membership number, then after you complete your first transaction you're eligible to receive the bonus. With this deal, Costco members are also eligible for quarterly rebates on all automatic transaction fees. As a regular gold-star member I'm eligible for a 10% quarterly rebate. Executive members are eligible for a 25% rebate. That covers the free money part.
Second, if you set up an automatic investment, it only costs $4 each time.
Third, if say, you've always wanted to invest in Berkshire Hathaway, but couldn't afford Class A shares (today around $140,000) and even find Class B shares (today around $4,600) a little pricey, you can purchase partial Class B shares through the automatic investment program. The symbol is BRK B -- although on other sites it may display as BRK.B or BRK-B.
(Berkshire Hathaway is Warren Buffett's and Charlie Munger's company. If that's not your cup of tea, you might try saving the minimum for a no-load index fund like one of the Vanguard funds.)
4-6 weeks later you'll have $70-$90 free money in your account, to do with whatever you like. The end.
Disclaimer: I am not any kind of financial professional and you should always do your own research before selecting a financial strategy. Also, this is just my opinion and I'm not paid by anybody for it.