One of the best ways to invest for the long term is to focus on reliable stocks with high dividend yields. Combined with a dividend reinvestment plan, these kinds of investments can grow exponentially as you accumulate more shares of a given stock without having to shell out your own cash. Dividend stocks, with the important exception of yield traps, also have a proven track record of returning cash to investors and delivering profits, giving investors an extra degree of security.

If you're looking for great dividend stocks, keep reading to see why these Foolish contributors recommend ExxonMobil (XOM -0.88%)GlaxoSmithKline (GSK), and Target (TGT 1.37%)

A woman looks up and smiles as hundred dollar bills rain down around her.

Image source: Target.

Bet against this big energy stock at your peril

Todd Campbell (ExxonMobil): If you don't own energy Goliath ExxonMobil yet, now could be the perfect time to add it to your holdings. The company's got some big production coming online over the next few years, and a recent downturn in oil prices has caused shares to swoon and its dividend yield to swell.

A diversified energy company, ExxonMobil explores, produces, refines, and markets oil and gas products. Its vast resources make it one of the world's biggest companies, and its production could begin climbing soon because new production offshore Guyana is expected to come online beginning next year.

Its massive Stabroek field offshore Guyana holds billions of oil equivalent barrels of resources. In fact, ExxonMobil currently anticipates that the play could produce over 750,000 barrels per day by 2025, beginning with 120,000 as early as 2020.

ExxonMobil's also a major player in arguably the most attractive shale formation in the U.S.: the Permian basin. Management thinks it can be producing 1 million barrels of oil equivalent per day in the Permian by 2024.

Certainly, renewables will produce a larger proportion of future energy, but oil and gas will continue to remain major sources of energy for decades. Given that the company produced $20 billion in free cash flow after investments last year and it paid out $14 billion in dividends despite arguably unfavorable market conditions, I think picking it up now when its yield is an attractive 4.6% could be smart.

The cure for your income ills 

Sean Williams (GlaxoSmithKline): If you're looking for a top-tier business with a high-yield dividend that you can preferably set and forget in your portfolio, look no further than U.K.-based pharmaceutical and healthcare products provider GlaxoSmithKline.

GlaxoSmithKline has three operating segments, and each brings something to the table that the other doesn't.

The first, Consumer Healthcare, features everything from oral health to nutrition products. Although this is a segment that usually grows at the slowest rate of the three, it generates the most predictable cash flow and offers reasonably strong pricing power. That's because most consumer health products, such as toothpaste, are basic-need goods and will be purchased regardless of how well or poorly the U.S. or global economy are performing.

The second operating segment, vaccines, has historically grown at closer to a mid-single-digit rate. This division is primarily designed to take advantage of a growing global population, which makes it an intriguing long-term play. Recently, though, GlaxoSmithKline has seen vaccine sales soar thanks to Shingrix, the most popular vaccine for the treatment of Shingles. Sales of Shingrix accounted for $457 million in first-quarter sales, or more than a fifth of all vaccines revenue, and it's still growing at an extraordinary pace.

The third and final segment is pharmaceuticals, which generated 54% of first-quarter sales. Although pharmaceuticals is the toughest to predict from a cash flow perspective, it offers the strongest long-term growth rate. Leading the charge are Glaxo's next-generation asthma and COPD medicines (Breo Ellipta, Anoro Ellipta, and Trelegy Ellipta, to name a few), and its portfolio of HIV therapies. In the first quarter alone, these new respiratory products brought in $807 million in sales (more than $3.2 billion on an extrapolated annual basis), while core HIV products hit $1.36 billion in Q1 sales ($5.44 billion in extrapolated annual sales). 

Add this all together, and throw in billions of dollars in established pharmaceutical sales that are still generating a boatload of residual cash flow, and you have a recipe for a 5.8% dividend yield and forward price-to-earnings ratio that's well below the average of the S&P 500. That's what makes GlaxoSmithKline a top high-yield stock to consider buying.

This retailer just keeps getting stronger

Jeremy Bowman (Target): Fresh off another strong earnings report, Target looks like a great stock to pick up right now. The big-box chain has remade itself and adapted to a new retail era, thriving while department store chains and other traditional retailers are struggling. Target is renovating its stores, is adding new small-format locations, and has launched a multipronged e-commerce strategy, complete with same-day delivery from Shipt and a pickup option that allows customers to get their orders placed into their vehicles once they pull up to the stores.

The results are clear. Comparable sales jumped 4.8% in the first quarter with a 4.3% increase traffic, following a similarly strong performance last year. Digital sales jumped 42%, with the bulk of the growth being driven by same-day fulfillment. 

Operating income increased 9%, and adjusted earnings per share jumped 15% to $1.53, boosted by share buybacks, and easily beat estimates at $1.43. Target declined to raise its full-year guidance, but based on its results and second-quarter EPS forecast of $1.52-$1.72, the company is tracking above the top end of its full-year EPS guidance of $5.75-$6.05.

Based on that range, Target is trading at a forward P/E of just 13, and dividend investors can sit back and collect a 3.3% yield. Even better, the company is a Dividend Aristocrat, and Target is expected to raise its dividend for the 48th year in a row in June. Considering Target's strong recent profit growth, investors could see a sizable dividend increase this time around.