How do I know if I gave a Best answer?
409344
You'll get an email & 10 points.  You can also check "My Q&A"
257951
when you choose a best answer, there is a box where you can type a message. You can say "Thank You" there.
204669
First, it depends on the question.  If I am asking for opinion, such as favorite television show, anyone who gives me their opinion has given me a satisfactory answer.  In such a case I will almost always pick the opinion that most closely resembles my own as best answer, or I will put it up for a vote.  If I am asking for information, however, a satisfactory answer will usually be one that actually gives me information.  The most helpful answer will be awarded the best answer.  The trick is when I am asking for an informed opinion, much like you are asking here.  A satisfactory answer must have at least a little thought behind it in such a case.  Picking a best answer is not as easy, either.  Sometimes I pick an aswer that most closely resembles my opinion.  Sometimes I pick an answer that has given me the most to think about.  Sometimes I pick an answer solely on how much effort the person put into answering.\n\nI should also note that for most questions an occassional funny response is always acceptable.  An insulting answer, however, is never acceptable.  Sometimes a truly funny answer will win best answer, especially if no other answer stands out.  Some questions, too, are just asking for funny answers.  If I ask "Can Superman see through Lead Crystal?" for example, I am probably not going to accept, "Yes, it's glass," or "no, it's lead."  However, I would love an answer like "Why do you think I pay $1800 for my windows and find 30 year old paint?"\n\nWell, that's just a little insight  into how my mind works... :P
412699
Often, especially in "Society & Culture", the person isn't really asking a question.  They are going to pick whoever agrees with their pre-determined answer.  So even when your answer is actually "best", it doesn't get picked.  Sometimes upsetting, though, I agree.  If it is a really ridiculous case, I'll usually leave a comment.
748054
Is it possible for you to pick this as the best answer?
495409
Click on the little Tab up top that says My Q&A\nYou can see your:\n\nQuestions\n\nAnswers\n\nAnswers chosen as best answer\n\nQuestions you are watching\n(When you're on a question, add it to your watch list). This is good if you find a question you want the answer to, but you don't know the answer to.
175127
Frist off 'Sing in'. They on the upper part of your page you'll find 'My Q&A'. Click it. it will show all the question tha u've asked and when you click one of them it will show you the answers that were given (if they were). Choose the best answer and then you can addd comment of tell him whatever u want to say.
211485
see the answer i already submitted
797526
Yea i do check my answers later, only\nthe importants one, just 2 see if i got\nthumbs up or down\nto c if ppl liked my answer or not!
227538
if you've asked a question, when you pick the best answer there is a spot to leave a comment on why you picked that one. That's the easiest way. Cuz if someone answers a question and it gets picked as the best, they'll see the points and check with question it was for and see the comment!\n\nwhew! that was wordy and long. I hope I made sense!
1058776
chose me as the best answer of this one
1069433
if noone answers you can i get best answer?
71500
It depends on what level you are on. Look at the point system and it tells you what level your on and how many questions you can answer on that level.
1160187
someone picking my answer as best (hint hint)
116252
Its easy to tell which answer is the best.
147500
Go to the question.  Not all questions are open to voting on a best answer.  The asker decides whether to accept votes or not.
1134861
The answer is still there. Just click on the "My Q&A" link to the upper right of any Yahoo! Answers page, and then click on the question title in your list. From there you can select the best answer for your question and even leave a short thank you to show your appreciation.