the fundamental thing to do before selecting keywords is to do market survey and understand what is needed... then ofcourse google adwords is good option
maybe you can use google eksternal tools, to get right keyword, and also you can use google insight search, and google related search.. good luck
Google adword is the best tool for keyword suggestion. If your site is new try to target such keywords in the beginning which have less competition and then target high competition keywords.
garaz hit the nail on the head. Keyword research is key, and it should be done BEFORE you ever decide on a product or service to promote. If the competition is overwhelming for the keywords I want to use I will pass. That is usually after several hours of keyword research, using the GKWT, Market Samurai, and what little common sense I have. After a while you get a "feel" for what keywords might work.
ansh1593, I understand your question. Keywords are a challenge for us all, and if anyone is not challenged by keyword research they are either naive or they outsource it! I look at keyword research like a treasure hunt, but without a map. I use several tools, and some intuition. If you get it wrong you will not find the treasure, and may work tirelessly trying to rank in the SERPs with no luck. Keyword research should be done prior to deciding on a product or service to promote. Once I find a potential product if I cannot find keywords that I can compete with I will pass. I look for products that have demand, and keywords that are relevant that people actually use to find this product, and these keywords must have manageable competition. You must get this right. you will never rank for page one with keywords like "car insurance" or "cameras". But maybe you can rank for a less competitive keyword like "underwater cameras". Make sense? I use the Google keyword tool, and Market Samurai to locate keywords that meet my criteria.
You can use Google tools to associated data queries, but do notchoose good or bad words, choose to do general word is very wise.