If your song has a single BPM, I recommend using BPM analyzer
viewtopic.php?f=10&t=1707If that does not work so well and you don't mind depending on other people, you can always post here
viewtopic.php?f=60&t=13795&st=0&sk=t&sd=aAs to how to time, here is how I do it. I listen to the song at 25% and try to pick out something is used to keep the beat, usually a constant drum beat. I set the offset to when I hear the first drum. Then I listen for the next drum. I set my BPM so that the second drum is on the second white line.Afterward, I listen for the 5th drum, and use the 5th drum to further fine-tune my BPM. Then I check to make sure the first few drum beats still fit the BPM. After that, I listen to more and more of my song and fine tune my BPM as I go, and every time I change the BPM, I go back to make sure the BPM is right.
If there is any section where the BPM seems incredibly off, I look for the start of that section and add another uninherited timing section there. Afterward I repeat the steps outlined above till I finish timing the song. If you need any clarification, feel free to ask.