Before you start working with demons you need to find a belief system that works for you. Once that has been established, you need to start off practicing the Basics. AwaketoLong has a great post on the basics and I think you should start off by reading this. Here's the link to his post. http://www.spellsofmagic.com/read_post.html?post=483942
Speaking from personal experience you really need to start with and master the basics before you even attempt to work with the Daemonic. Evocation and sigil magick isn't something I would recommend jumping into if your new to magick. Depending on what interests you I'm going to leave you with a list of my favorite books regarding this topic. These books are good for Beginners when it comes to working with Daemons and Daemonic magick. Each one that is listed has the basics in them and will help guide you towards your goal.
Summoning Spirits - By Konstantinos
Nocturnal Witchcraft Series ( Nocturnal Witchcraft, The Gothic Grimoire and Nocturnacon) By Konstantinos
The Daemonolater's Guide to Daemonic Magick- S. Conolly
The Complete Book of Daemonolatry- S. Conolly
Works of Darkness- E.A. Koetting
Evoking Eternity- E.A. Koetting
Beginning Luciferian Magick- Michael Ford
Luciferian Goetia- Michael Ford
These are just a few of the books out there that I have read through and worked through with decent results. These books are newb friendly since they have a workable system that starts you off with the basics before they move on to more complex topics towards the end of each book.
In my honest opinion I would start off with Konstantinos work because he has the safest approach out of all the authors I listed. Conolly is the same but her work is approachable if your looking for a system that worships the Daemonic as Deities. I would be cautious when approaching Ford's and Koetting's work. Ford approach really doesn't involve any banishings or protection against any harmful spirits but I haven't seen anyone suffer any backlash due to his system.
Koetting is another story when it comes to this. His methods work but I've met quite a few people who have suffered hauntings and oppression due to his work. I have not experienced this and I have worked through all of his books. Either way I suggest finding something that interests you regarding this topic and I'm sure others will list some great books to start off with if this is your goal.