One common bit of financial advice is to invest in what you know. Sometimes, however, you may not know what you know. There are stocks you likely use every day, but they may be hiding in plain sight.

These can be great companies to invest in because their products are so common, yet because they are not as well-known as, say, Apple or Microsoft, they may also be underpriced, providing a nice opportunity for savvy buyers.

You may already be using TE Connectivity (NYSE:TEL), Conagra (NYSE:CAG), and Fiserv (NASDAQ:FISV) every day, so why not invest in them?

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Check your thermostat or under the hood of your car

Chances are, if you drive a car or own a household appliance, you benefit from the technology of TE Connectivity. The Switzerland-based connectivity and sensing company has more than 78,000 employees and had $13.5 billion in revenue last year. The company makes sensors, cable connectors, fiber optics, EMI filters, antennas, resistors, transformers, relays, and switches -- pretty much everything that any high-tech device needs to run. 

The company certainly wasn't immune to the crash caused by the coronavirus pandemic, as its shares are down more than 15% year-to-date -- but they're up more than 30% over the past three months. Looking at it long-term, if you had invested $1,000 in the stock 10 years ago, you would have nearly $4,000 today, not counting earnings from dividends.

There are plenty of other positives about the stock. This past May, TE Connectivity raised its dividend for the eighth consecutive year, and according to Barron's, it was one of 11 S&P 500 companies to do so in the month. The new quarterly dividend of $0.48, an increase of 4.4%, works out to a yield of 2.4% with a safe payout ratio (trailing 12 months) of 34.6%.

It's also poised to do well as the 5G revolution takes off, as its ERFV coax connectors and high-speed stacking connectors will be crucial for devices to benefit from 5G technology.

Conagra is recession-proof because people have to eat

You may not know Conagra Brands as a company, but you almost certainly know its brands, which include the consumer staples Birds Eye, Bluebonnet, Marie Callender's, Healthy Choice, Mrs. Paul's, Peter Pan, Chef Boyardee, Duncan Hines, and Egg Beaters, among many others. Chances are, you have several Conagra items in your pantry. The company has done well during the coronavirus pandemic, because people are eating more of their meals at home.

But Conagra was doing well before the pandemic hit, too. It reported that its organic sales were up 21.5% in the fourth quarter and its full-year sales were up 5.6%. The company's biggest climber was its food staples division, which reported a 46.3% rise in sales.

Its shares rose by 3.4% over the past year, and it has increased revenue now for four consecutive years. Another nice plus is the company's $0.85-per-share quarterly dividend, which offers a 2.4% yield.

You don't realize how often you use Fiserv

Fiserv is a global leader in payments and financial technology. Whenever you pay a bill online or transfer funds, the chances are your bank or merchant is using Fiserv technology. Fiserv boasts 34 consecutive years of double-digit adjusted earnings-per-share (EPS) growth, and it has thrived despite the pandemic. Outgoing CEO Jeffery Yabuki says that during the last quarter, it added 36 new customers in e-commerce, such as Total Wine and Regis Salons.

The company's stock is up more than 4% over the past year and more than 10% over the past month. An important move for the company came when it bought payment processing company First Data for $22 million last year. Not only did it find its new CEO in First Data's Frank Bisignano, who took over for Yabuki on July 1, but management said Fiserv had broadened its business model and growth opportunities and found cost-saving synergies with the acquisition.

The company reported that it doubled its annual revenue last year. In the first quarter of this year, the company said its GAAP revenue was up 151% and its net income was up 67.5%, compared with the same quarter in 2019. Earnings per share rose 16% year over year as well. 

Everyday products with better-than-everyday returns

Of these three, Fiserv has had the most steady consistent growth, and that's likely to continue as we all become more dependent on online payments and online banking during the pandemic. Conagra is also steady, with revenue growth over the past four years -- and this year, as well. TE Connectivity shows the most potential for growth of the three because its shares have been depressed a bit by the pandemic and because of the company's crucial role with 5G technology.