The way native English speakers commonly use these words are as follows: -boring = the opposite of interesting. A boring lecture, for example, makes you want to fall asleep or walk out. This is a standard word (not slang) -lame = the opposite of 'cool' or 'trendy' or 'great', but it can sometimes overlap with the above meaning to mean 'not interesting', or, when describing an excuse, it can mean 'not convincing enough'. This is a slang use of the word. But you should really be careful with this word. Although it means 'uncool' or 'not good' when used in slang, it's original meaning refers to physical disability; so using such a word to describe things negatively would be considered offensive by some people and in some contexts. But of course this is something that native speakers would argue about and ultimately you need to make you own mind up about how you use this word, keeping my warning in mind.

Boring is not interesting or exciting. Example: That girl is boring as she never has ideas of things to do. That book was so boring I fell asleep reading it. Lame in this sense is unsatisfactory or dull. Example:The movie at the theatre was lame compared to the talk about it. The girl's attempt to be fashionable was lame.