Gather information. Often a list of essentials for an experimental procedure are listed and handed out to students. This can provide clues to document the procedures in a lab report. Any information you may have jotted down during the procedures themselves will lend credibility to the process and help you envision what was done.
Outline events. Write out what you initially remember having done in the experiment in a numerical list. Since many professors don't provide a procedures list in advance, most of this writing must be done from memory or with little reference to in class documents and the text. Outlining the basic steps you can easily recall will make this task a lot less difficult.
Add detail to steps. This includes describing both quantitatively and qualitatively what was done in the process. How much of what solute or solvent was added, what pieces of glassware or tools were used in each step, and description of how each step was executed can be especially useful. Indicating whether certain steps were skipped, augmented or altered can also be helpful to the depth of such a report.
Check procedures with text. If a lab manual or similar experiment is available either from your professor or online, be sure to check your procedures against initial processes. This may help you remember something you have done or aid in further elucidating procedures that may otherwise be difficult to explain in a report.