You’ll need to decide a couple of things first -
1. The total number of addresses you need – the 192.168.x.x is suitable for smaller networks( 255 x 255 systems), but the 10.x.x.x is also available for the largest internal networks.
2. Next is are their certain systems that you want to avoid giving access to others. I normally take all major systems and put them on separate networks and block access, for e.g., network devices are on a separate IP addressing scheme, so also for servers etc.
3. Are systems going to have fixed IP addresses or dynamically allotted addresses
4. Lastly and most importantly system naming conventions need to handled carefully and consistently – e.g., I avoid giving server names based on either function or location, any arbitrary name works. Use aliases for function based naming etc. which can be switched easily. Thus MailSvrOne can be easily moved around without the user knowing the administrative details.
Hope this helps you start