First click the Create button located at the bottom of your profile page (or use this link right here https://plus.google.com/pages/create ).
Once your there, select your relevant information.
After you have selected what type of page you want, you will be brought to something similar to the page below, I have chosen product or brand for SEO Positive. Different categories require different information but is should be fairly standard.
In the Page Title section, you can fit in roughly 8 words, for best practices, put your company name first followed by your most important keywords. If you want to make it look professional add a few pipe signs a.k.a vertical line, to separate your keywords a little. Then add the appropriate information.
The next is the tagline and profile picture, again this is similar to the title but you have a space of roughly 10 words to describe yourself so make sure you put your 10 most important search terms, including your company name if you wish to establish yourself as a brand.
At this point you're given the option to share the page via your profile and your page is available for the public to see. But you just have a few more things to do, just to fine tune your page and give it that extra boost in the rankings.
You have 4 different fields here; if you have already entered your website, you are down to 3. The first and possibly most important is the introduction. This is an area that you can introduce yourself and your company, outline why your company is on Google Plus and what you hope to achieve from being on the network. Use your keywords but don't go overboard.
Finally we have the phone number and recommended sites, these do not have any immediate optimization value although the telephone number may help with local .
The optimization I have done on my profile has proven to be a great success. Imaginably, SEO is a very competitive industry and the key phrases are no exception, due to the masses of other SEO companies, it can be quite difficult to rank. Without a doubt there are other factors and from my previous research, things like circles and amount of content posted definitely affect rankings, but that is another story.