Exchange-traded funds offer a convenient way to invest in sectors or niches that interest you. If you'd like to add some gold-related stocks to your portfolio, the iShares MSCI Global Gold Miners ETF (NYSEMKT:RING) could save you a lot of trouble. Instead of trying to figure out which companies will perform best, you can use this ETF to invest in lots of them simultaneously.

The basics
ETFs often sport lower expense ratios than their mutual fund cousins. The iShares ETF's expense ratio -- its annual fee -- is a rather low 0.39%. The fund is fairly small, though, so if you're thinking of buying, beware of possibly large spreads between its bid and ask prices. Consider using a limit order if you want to buy in.

This ETF is too young to have much of a track record to assess. It's down more than 40% over the past year, though. As with most investments, of course, we can't expect outstanding performances in every quarter or year. Investors with conviction need to wait for their holdings to deliver.

Why gold?
Gold is not everyone's cup of tea, but some investors like to include some in their portfolios for the sake of diversification. Some also favor precious metals, as some of them have more utility. With gold's recent plunge, some are steering clear, while others are seeing bargains.

It wasn't a pretty past 12 months for gold-related companies, due to falling gold prices, rising costs, and even some labor difficulties around the globe, along with a strengthening dollar.

AuRico Gold (UNKNOWN:AUQ.DL) plunged 44%, having posted some disappointing results lately, and is also suffering from a competitive disadvantage, with its costs above those of some peers. On the plus side, though, the company recently initiated a dividend, which now yields about 2.8%.

Kinross Gold (NYSE:KGC) sank 40%, and yields about 3%. It has some worried, with its rising debt, and recently negative free cash flow. Its stock has been setting some multi-year lows and, while its earnings are in the red, its revenue has been growing steadily over the past few years. Last year, management committed itself to quality over quantity -- and delayed some mining projects.

Randgold Resources (NASDAQ:GOLD) shed 19%, despite posting record production last year. The company has significant operations in Mali, which has been in the midst of considerable political upheaval. Still, its sizable African operations are promising. The company recently hiked its dividend by 25%,

Yamana Gold (NYSE:AUY) fell 18%. It recently yielded 2%, and it has been upping that payout significantly. Bulls like its conservative management and relatively low costs, and have high hopes for its recently acquired Cerro Moro mine in Argentina.

The big picture
A well-chosen ETF can grant you instant diversification across any industry or group of companies -- and make investing in and profiting from it that much easier.

Longtime Fool contributor Selena Maranjian, whom you can follow on Twitter, has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.