The people talking about needing to go with a group are giving outdated info. You can travel solo now. You DO need to fall within one of 12 authorized categories, but you no longer need to get any paperwork to prove this, you simply "self authorize" - you declare on a form that you're going for "professional research" or the like. It couldn't be easier. I went two months ago. Many cities have direct flights, and they're super cheap, my direct flight from LAX was only $300 roundtrip on Alaska. After you book your airline tickets, you'll need to get a visa through Cuba Travel Services, a licensed company in the US. It's about $80, as I remember.
You can book accommodations at countless apartments directly through AirBnb online. The only hotel you can book from the US directly is the Four Points Sheraton, which is way in the suburbs, in a terrible location. However you can book many other hotels through Cuba Travel Services. I don't work for them, haha, they're just one of the few companies licensed by the Cuban government and the US government. A nice AirBnb in Havana will run about $150-200 a night. A nice hotel room will cost more, running from about $300-500 a night. I'm not talking Ritz Carlton-level, that simply doesn't exist there. The hotels are all around 3-4 stars by American standards. I chose a hotel for most of my stay, so I'd have the advantages of a concierge, 24-hour staffed front desk, excursion desk in the lobby, restaurants, 24-hour cafeteria, etc.
Be aware there are two currencies in Cuba, one for foreigners/tourists that's used in all hotels, restaurants and museums (CUCs) and one for locals that you'll never encounter most likely (Pesos), and neither can be taken out of the country. American credit/debit cards will NOT work there. Bring enough cash for your ENTIRE trip. Cuba is EXPENSIVE, I recommend minimum $100 per day, $150 per day if you want to feel safe, on top of lodging costs. Ideally, go to a currency exchange office before leaving home and bring your cash into Cuba in Canadian Dollars or Euros, there is a 10% penalty to convert US Dollars into Cuban currency.
Your phone will most likely not work at all down there. Verizon has almost no coverage. If you have Verizon, your phone will be able to send and receive texts only for the first two days or so, then it will lose all reception, except possibly the ability to receive incoming calls. I heard rumors that Sprint and T-Mobile, might have reception, and that it's possible to install a Cuban SIM card and have coverage, but honestly I enjoyed being cut off, is I didn't investigate.
Cuba is incredibly safe for tourists, there's almost no street crime. There is a great deal to see, Havana is beautiful, and can easily fill a week, without even starting on daytrips. The top daytrips are to Vinales, a scenic valley, and Varadero, a beach resort. Trinidad is a pretty colonial town, too far for a daytrip, you need a day to get there, a day to see it, and a day to get back.
See it now, while it's still stuck in a timewarp in 1959, it's unforgettable and the people are welcoming. Be prepared, very few speak English, but you'll be able to manage it if you know even just a few phrases in Spanish, and they're always eager to help.
Cuban customs won't look at you twice, they just want as many tourists as possible to bring in revenue, and US Customs also didn't ask anything other than whether I'd come into contact with farm anilams, due to possible diseases. There were no questions about my "self authorization".
Have a great time and enjoy!