Every investor has different financial goals and time horizons, so a strategy that works for one may not work for another. Yet it pays to follow what stocks some of the top investors in the world are buying and selling -- and why they're doing so -- as that can not only help you dig up fresh stock ideas to research, but it can also help you better understand the companies whose stocks you own.

With that in mind, we asked three Motley Fool contributors to each pick a stock that some of the smartest investors on Wall Street are buying right now and tell us whether they're worth your money. Here's what they have to tell you about utility Xcel Energy (XEL -0.61%), industrials conglomerate Dover Corp. (DOV -0.05%), and cloud marketing leader HubSpot (HUBS -0.79%).

A thinking man with a light bulb above his head.

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A renewable energy leader with momentum

Maxx Chatsko (Xcel Energy): In mid-October, electric utility Xcel Energy issued a press release arguing that shareholders should reject a mini-tender offer from TRC Capital. The investment firm had reached out to shareholders and offered to purchase their shares (for below market value). If successful, TRC Capital would end up owning 0.49% of Xcel Energy.

No matter how that process shakes out, investors with a long-term mindset might agree with TRC Capital that there's an opportunity here. The $24 billion utility has grown into a leading renewable energy advocate in the last 10 years. After relying heavily on coal-fired power plants for most of its history, Xcel Energy is on track to generate 45% of its electricity from renewables by 2027.

That's great news for the environment and investors alike. As Xcel Energy has discovered, wind farms and solar facilities don't require fuel purchases, which makes well-sited renewable assets big profit generators compared to coal- and natural gas–fired power plants.

It may not seem like much, but avoiding fuel expenses frees up considerable cash flow for growth investments. Consider that fuel purchases comprised 47% of all capital expenditures in 2010, but a bevy of coal retirements and renewable project start-ups are expected to drop that to just 28% by 2027. That should accelerate growth for the business (and renewable energy) and allow Xcel Energy to continue growing its 3.2% dividend yield for the long haul.

A conglomerate realigning operations for the better

Neha Chamaria (Dover Corp.): Dan Loeb and his hedge fund Third Point, which has nearly $17.5 billion in assets under management, has owned a stake in Dover Corp since the third quarter of 2017. An activist investor, Loeb mainly wanted the industrials conglomerate to separate its energy business to reduce cyclicality and unlock greater shareholder value from its core industrials segments.

Loeb has closely engaged with Dover since and even bought another 80,000 shares during the second quarter this year. In between, the company has restructured its operations, even spinning off its upstream energy segment as a stand-alone business now listed as Apergy Corporation (APY). That leaves Dover with three broad businesses to handle: engineered systems (industrials and fast-moving consumer goods), fluids (pumps and filtration systems), and refrigeration and food equipment. That means Dover is still a well-diversified company minus the volatility associated with energy.

Dover believes it should be able to generate operating cash flow worth nearly $2.5 billion to $3.5 billion between 2019 and 2021, leaving it with ample capital to deploy on organic growth and bolt-on acquisitions while continuing to reward shareholders. For perspective, Dover is among the handful of companies that has increased dividends every year for 60 years or more. Management intends to maintain a conservative payout of 30% but grow dividends annually by 2% to 4% through 2021 alongside share repurchases.

I foresee Dover growing its operating income by high single-digit or even double-digit percentages in the long run as its restructuring efforts bear fruit. The company already has an incredible free cash flow (FCF) conversion rate (the percentage of net income converted to FCF, the higher the better). With analysts projecting Dover to grow its earnings by nearly 14% annually over the next five years and management committed to growing dividends, the stock looks like a great investment for the long haul.

A small cloud-computing platform play with a big opportunity

Chris Neiger (HubSpot): HubSpot, a cloud-computing marketing platform company, has gained the attention of lots of investors as its stock has skyrocketed about 50% over the past year. And the hedge fund created by billionaire investor George Soros, Soros Fund Management, reported in its most recent 13-F filing that it too is now betting on HubSpot.

If you haven't heard of HubSpot, the company helps other businesses connect with their customers through marketing services, including lead generation, blogs, content management, customer relationship management, and much more.

The company's sales in the most recent quarter were up 38% year over year to $122.6 million, and earnings per share hit $0.18, up from $0.07 in the year-ago quarter.

HubSpot's business is built on the freemium model, which means that it allows potential paying customers to use a variety of its services for free and hopes they'll upgrade to more robust services later. So far, the strategy appears to be working, and in the second quarter, HubSpot's subscription revenue was up 38% year over year.

So should investors follow Soros's fund and pick up HubSpot shares for themselves? I think it could be a wise move when you consider that the company increased its total customers by 40% year over year in the most recent quarter and expanded its operating margins to 5.3%, up from 2.7% in the year-ago quarter. Add all of that to HubSpot's sales and earnings growth, and this company looks like a tempting marketing platform play.