This is the most accurate website for Kratom.
http://www.sagewisdom.org/kratomguide.html I buy mine here too. It is a little more expensive, but well worth it..
Kratom in low doses is a stimulant, and rather nice. At higher doses, you start to get the Opiate like effects. Although not a true opiate, it has many of the same properties, with the addiction value as well.
I have done it 3 times. The first was way too much. I got severe sweats 30 min after taking it. The nausea is really bad at high doses. I did not vomit, but the other 2 that I shared it with did. I had to lay down, and this is where Kratom is great. Go to a quiet place, take your dose, put on some music, and just lay back. Closing eyes gets rid of nausea 100% for me.
It is really easy to prepare. Just crumble the leaf, add it to 2 L of water, bring to a boils and let it evaporate down to about 100ml. Repeat with clean water and combine the two strain the leaf off, boil down more if you like. Depending on the amount used to make the extract that will be the size of your dose(s).
Be prepared, this is some of the most vile crap ever. It is bitter, and nasty. Do not add sugar, it makes it worse! I just evaporate mine so I only have like 1/2 oz per dose. It gets really think, but is easier to wash down with a shot of vodka or something.
Read through the guide and ask me anything else. Cheers.