I have come across a sentence "I was talking about the fourth quarter of game seven, when you're looking to lockup a championship...". I checked in all available dictionaries and did not find meaningful explanation. From a context I guessed it means to win a championship prematurely according to some tournament system, but there are still doubts. Also Google returned me a page that said "Porsche Looking to Lock Up World Championship in Shanghai" without verb be before "Looking". So my questions are: did I guess the meaning correctly and what is correct grammar to use the expression (with/without be)?
You have it right: "when you're looking" has the verb to be before looking. The headline "Porsche Looking to" leaves out the word is, and it means they are seeking to complete the championship by winning it solidly: The auto maker is in pursuit of a quick finish to the race
Definition of Look 2.c. To turn one's expectations:
looked to us for a solution.
Both your examples have the same meaning: aiming to (looking to) achieve or own (lock up).