It's pretty clear -- bear markets are tough. And today's bear market probably isn't putting you in the best mood for investing.

But there's actually something very useful you can do right now. You can prepare for the next bull market. We don't know when it will arrive, but history tells us tough market times always are followed by brighter days.

How can you prepare? Invest in companies with great businesses and future prospects. Why get ready now? Because shares of so many solid companies have tumbled into dirt cheap territory. And right now, I can think of three with potential to make explosive gains over time.

Wall Street forecasts double-digit share-price increases for each in the coming 12 months alone. Let's take a look at these exciting stocks to consider adding to your portfolio right now.

1. Amazon

Amazon (AMZN 0.22%) has disappointed investors over the past few quarters. Rising inflation and supply chain disturbances have weighed on earnings. That's led to Amazon dropping 30% so far this year.

But it's important to take a glance back into the past and a look ahead to the future. As for the past, Amazon has a solid track record of revenue and profit growth. The company also has grown important metrics, such as return on invested capital and free cash flow (until recently).

Now let's focus on the future. Why can Amazon return to the solid performance of the past? It's dominance in two key businesses: e-commerce and cloud computing. Today, higher inflation is hurting e-commerce. But retail e-commerce is forecast to grow in the double digits this decade. And Amazon, as a leader, is perfectly positioned to benefit.

As for cloud computing, we don't even have to wait to see performance there. Growth hasn't stopped. Amazon Web Services (AWS) reported double-digit growth in revenue and operating income in the second quarter and continues to sign new contracts and expand worldwide.

Today, Amazon shares are trading near their lowest, in relation to sales, in about five years. At the same time, revenue continues to climb. So the best deal on Amazon right now may be its shares.

2. Moderna

Moderna (MRNA -1.52%) soared in 2020 because it developed a coronavirus vaccine. Currently, that status as a vaccine stock is dragging down the shares because investors are worried about a drop in revenue when the pandemic shifts to an endemic situation.

But even with a decline in vaccine revenue, Moderna looks like an attractive long-term buy. First, vaccine revenue won't disappear. The company says the U.S. coronavirus-vaccine market alone could be worth as much as $13 billion post-pandemic. Leader Moderna surely could carve out a decent share there -- and internationally, as well.

The company already won authorization for its first strain-specific booster. And it's working on a combined coronavirus-flu-vaccine candidate for use further down the road.

Second, Moderna's vaccine fortunes have given it the cash it needs to develop other potential blockbuster products. I'm thinking of three phase 3 candidates: investigational vaccines for flu, respiratory syncytial virus, and cytomegalovirus. The first two may launch in the coming two to three years if all goes smoothly, Moderna has said.

All of this means that, yes, Moderna will continue to generate revenue in the area of coronavirus vaccination. But the company is only getting started when it comes to revenue through its other programs. Considering this, the shares look like a bargain today after dropping nearly 50% this year.

3. Nike

One of the things I love about Nike (NKE 1.72%) is its brand strength. And another thing I love is the company's success at transforming itself into a digital and direct-to-consumer player.

First, let's talk about brand strength. Nike has sponsorship contracts with some of the world's top athletes. That's a big way of connecting with sports fans and keeping the Nike name in the spotlight.

The Jordan brand is a key example. Basketball legend Michael Jordan retired about 20 years ago. Yet Nike's Jordan brand continues to be a slam dunk when it comes to revenue. The 2022 fiscal year was the Jordan brand's biggest ever.

As for Nike's transformation, it began in 2017. The company decided to focus on connecting with fans on its digital platform and selling directly to them through that platform and Nike stores. And it's working.

In the most recent quarter, excluding currency exchanges, Nike's direct sales climbed 14%. And Nike brand digital sales advanced 23% if we exclude the currency impact.

Today's economic environment is weighing on Nike. The company reported higher inventory and lower gross margin in the latest quarterly report. But these short-term problems don't tarnish the long-term picture.

Nike shares trade for 30 times forward earnings estimates. That's down from more than 48 late last year. At the same time, revenue continues to rise. Nike today looks like a bargain -- and one that could score investors a home run over the long term.