5 things to watch out for when Uber, the world's most valuable private tech company, goes public today

Uber will go public on the New York Stock Exchange on Friday morning, with an expected IPO price of $45 a share, at the lower end of its range.The company is making its blockbuster debut at a turbulent time for the markets. It's the biggest tech IPO since Facebook in 2012, even in a year of hot tech startups going public.We've listed out the five things to watch when the market opens.Visit Business Insider's homepage for more stories. Uber will make its debut on the New York Stock Exchange on Friday morning, marking several milestones at once.It will be the biggest tech IPO since Facebook floated in May 2012. The ride-hailing giant is likely to maintain that record through 2019, even though this year heralds a bunch of hot tech companies going public, including Lyft, Slack, Zoom, and Pinterest.It is also currently the biggest private tech company in the world, with a valuation of around $82 billion as it prices its IPO at $45 a share. At one point, the company had aimed for a valuation of $100 billion.Read more: Uber chose the worst possible week to have its IPO, and the bad timing will cost it billionsThe company is still best known for its core service: you open the Uber app and summon a private hire cab to get you quickly and comparatively cheaply to your destination. That service has evolved considerably, bringing in bicycles, scooters, food delivery, and public transport. It's also dabbling in driverless and even flying cars.That evolution, and global regulatory battles, have come at a price. Uber remains deeply unprofitable, reporting a loss of at least $1 billion in the first three months of this year on revenues of just over $3 billion.As the ultimate unicorn goes public, here are the five things to watch for:Where's Travis？The New York Stock Exchange marks the open and close of trading for the day with the ringing of several bells.An honour that's occasionally conferred on celebrities, heads of state, and company executives is getting to be the person that pushes the button to ring the bells. It's common, when a high-profile company floats, that the CEO and key execs ring the bell in a symbolic moment of achievement. Mark Zuckerberg rang the bell when Facebook went public, as did the three founders of Snapchat when Snap floated.When tech companies go public, it's often founder-CEOs who are ringing the bell. Uber is a little different since its founder-CEO Travis Kalanick exited the company in disgrace in 2017 after a string of company scandals. The two other cofounders are Ryan Graves and Garrett Camp, and all three remain shareholders in the company.Axios reported that Kalanick has been invited to the floor of the NYSE, but won't be the one ringing the bell. It isn't clear if he's actually attending — and if he does, it'll be worth watching his facial expression.Will Uber successfully avoid Lyft's pitfalls？The Wall Street Journal took a fairly technical look at what happened during Lyft's disappointing debut, and whether Uber can avoid the same pitfalls.According to the report, famed investor George Soros bought a 2.7% stake in Lyft from Carl Icahn, but hedged the stock before buying the shares. According to the Journal, that created a supply of shares which pressured the stock. There may have been similar trades.Uber will be looking to avoid these kinds of loopholes and ensuring its early investors keep to a lockup period, preventing them from suddenly dumping their stake.Whether the stock 'pops'A stock “pop” is when a company's stock begins trading higher than the IPO price. So a 15% pop on Uber's stock would mean the stock quickly begins trading on day one at $51.75.A pop is often taken a sign of demand and confidence in the company and can be indicative of long-term performance. (Not everyone likes the obsession with stock pops, and anyone who thought Facebook would do badly because of its relative lack of pop was evidently wrong.)What Lyft's share price is doingLyft's share price is down almost a third since its trading debut in March. That signals wider investor worries about the ride-hailing industry, and has cast a shadow over Uber's IPO. If Lyft is continuing its downward trend during Uber's debut, it's probably a good indicator of where Uber's stock will end up.Who's getting rich off the IPOOnce Uber's stock begins trading, we'll have a better understanding of who's getting rich off the company's debut and by how much.We already have the full list of the biggest shareholders but, until the company actually starts trading, we don't know how much their stakes are potentially worth. The list includes Uber founders Travis Kalanick, Garrett Camp, and Ryan Graves; CEO Dara Khosrowshahi; and Benchmark Capital among others.Most of the individuals will be paper billionaires, given Uber's biggest shareholders have agreed to a six-month lockup period. Should Uber's stock price trend down, their stakes will be worth less.