Tips: Important tip is to use same amount of soy sauce and sugar.
If you do this a day ahead, reduce soy sauce.
And don't forget to put it in a refrigerator.
Ask a butcher to slice the beef very thinly.
Traditionally, bul go ki made with very thin slice of beef.
But store bought beef, rather thick slice works as well.
Or there's a sliced beef just for bul go ki in a Korean grocery.
You can grill this on a table top, with a shallow pan.
Grill with medium high heat and have the juice of beef and vegetables on rice.