I find that that Google Keyword Tool is good enough for me. Then i start branching out into more in-depth keyword variations and LSI from that point on.
Yep, Google Keyword Tool is great. Learn how to use it. Remember, you can search on multiple keywords at once, too. Spend time experimenting with the options and filters, so you can fine tune searches to your requirements. Remember, Exact match type needs selecting to get an accurate reflection of traffic (it's amazing how many people make this mistake).
Yes I am agreed with you. I would also suggest you Google keyword tool to get large amount of synonym keywords..
I use the online dictionary to find synonymous. Look at googles searches related to at the bottom of the page also.