For the purpose of commercial insurance, they will generally look for a sum insured for office contents and its up to you to ensure that what you want covered falls into that amount. With laptops, mobiles, pda's if you want them covered you would need to mention them specifically on the policy as cover is not automatically provided. You would also need to cover your hardware such as servers and any increased cost of working if the data was lost and software, etc had to be re-installed.
If you're looking for EL/PL as part of it, you will need an idea of your projected turnover and wageroll (split by the category of employee depending on your business!). Obviously theres other things that can be included. If you need any more info, feel free to PM me. I work in that line of business.