Dream Incubation
If you're trying to get into a specific scenario as soon as you start dreaming, such as going into a PR, you're most likely looking to incubate a dream. If you previously looked into reality shifting, these steps might look familiar to you!
Procedure
Set your intention to go into this particular dream. Chances are, if you're here, you're off to a good start. Make the decision. Solidify it to yourself somehow if you feel that's necessary (it really isn't).
Relax your mind. A common way to do this is meditation. Coincidentally, this will probably help you get to sleep!
Visualize yourself in your intended dream. Take in all the details and put yourself in.
Perform autosuggestion by using mantras. Pick a phrase that expresses your intention, or a critical part of it, and repeat it verbally or in your head, over and over and over. This is optional but it is reported to help.
Reinforce the autosuggestion with writing or drawing. You should probably skip this step during WBTBs.
Go to sleep. Keep your intention in mind.
Notes
An alternative to this technique is to switch to your desired dream when you're lucid.
Further information
Evolventity's Dream Incubation Tutorial on Dreamviews
Enlighten Your Brain with Dream Incubation Techniques, an article on Medium by Jean-marc Buchert