Is there a word/phrase for locking one's hands to give someone a boost? I remember when playing as a young child, we would lock our hands to let another use it as a step (I'm not sure if I'm describing this accurately) to reach something high.
You have it exactly right.
"Could you give me a boost, please?"
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
Locking fingers is doing this: http://sphotos.ak.fbcdn.net/hphotos-..._3628635_n.jpg
In BrE, we also refer to "giving someone a bunk-up". I can't think of a word to describe what you actually do with your hands though. The whole process is just known as a "bunk-up" or a "boost".
If you're getting on a horse, it is called giving someone "a leg up."