Investors in TripAdvisor (TRIP 1.59%) haven't found much to celebrate in the company's last few earnings reports. While the world's largest online travel site is setting records for user engagement and reach, it hasn't been able to use that platform to deliver robust growth. Instead, sales have been near flat in its core hotel-booking segment since 2017.

Management back in May warned investors to expect sluggish results in the fiscal second quarter. But it will be even more important to follow what TripAdvisor has to say about growth trends for the second half of the year, since those will show whether the company is on track toward its longer-term targets.

Here are a few of the key trends investors will be following when the travel giant posts its earnings results on Thursday, Aug. 8.

Hotel booking 

The encouraging growth rebound that TripAdvisor posted at the end of 2018 didn't carry through into the first quarter of 2019. Instead, sales in the core hotel-booking business were flat, which led to falling revenue overall rather than the 2% increase that Wall Street was expecting.

A couple check into a hotel.

Image source: Getty Images.

Prospects aren't much better for the second quarter, since CEO Steve Kaufer and his team noted sluggish booking demand in international markets in the first few weeks of the period. Sales gains will also be held back by TripAdvisor's efficiency efforts, which involve being more cautious about marketing spending. These changes are reducing traffic to the website and keeping sales close to flat, but making the hotel business far more profitable.

Great experiences

The story is different over on the "experiences" side of the business, which includes bookings for attractions, restaurants, tours, and other travel activities. That division is seeing robust growth, with revenue rising 35% last quarter after accounting for foreign currency shifts. There appears to be a long runway for further gains, too, as TripAdvisor is still finding many more activities to add to its base.

So keep an eye on experience sales growth, but also watch whether the portfolio of bookable experiences continues to expand at about the 100% rate investors have seen over the past year. That segment isn't consistently profitable yet, and in fact losses worsened in the first quarter. Yet TripAdvisor might eventually see lots of good growth from this attractive sales niche after it scales up to full size.

Outlook updates

TripAdvisor said in May that it was on track to deliver double-digit adjusted earnings growth to mark an important step forward in its rebound plan. The company's longer-term outlook calls for sales to rise at about the same pace, though the first half of the year won't show such strength. Instead, most investors who follow the stock predict revenue will rise by just 3% in the second quarter after falling slightly in Q1.

That poor recent track record will put the focus on TripAdvisor's updated outlook for the second half of 2019. If management sees things going to plan, then firmer booking trends should position it to start making steps toward faster sales gains in 2020.

On the other hand, weak results would set investors up for a fourth consecutive year of near-flat revenue results. Granted, TripAdvisor has materially improved its annual earnings during that time. But the stock isn't likely to return to market-beating status until sales growth trends speed back up toward 10% or better.