Flight
Travel to Japan usually entails landing in either Narita or Haneda airports in Tokyo area. Sendai also has an airport for domestic and a few international flights (Korea and Taiwan). If you fly into Sendai airport, you'll most likely fly into Tokyo then take a domestic flight to Sendai.
Train
Travel in Japan is very convenient and easy but can be expensive. The Japan Railway Pass (JR Pass) allows you to take any JR trains and buses, including bullet trains, within a specified window (7, 14, and 21 days). If planning on travelling and sightseeing, it may be worth to buy a pass.
Travel Note
When we fly to Japan, we usually fly into Narita or Haneda airport. From Narita airport we usually take the Keisei Ueno line to Ueno. It's cheaper and faster than Narita express, which would bring you to Tokyo station, passing Ueno, then have to travel back up again. From Ueno Station, we usually take the bullet train to Sendai - Tohoku Shinkansen Line. (**Keisei Ueno line is not covered by JR Pass. Narita Express is covered by JR Pass) From Haneda airport, we would take regular JR lines in Tokyo and make our way to Ueno Station for the same bullet train.
Hotel
Hotel stays in Japan can be expensive, but there are a number of business hotels that are affordable. We usually use Toyoko Inn, but there are many others if you do a google search. Capsule hotels for the adventurous ... AirBNB and house rentals are also possible if you search, but probably won't be as many in Sendai.