One thing most people say is that Britain is a trading nation and they hope the UK can remain a member. However they then go on to make various conditions, saying it must be in the UK's interests to remain and depending on their viewpoints these conditions vary in strictness.
For economists the question is about the gains from trade. The lower the barriers to trade the more everyone benefits. There are various grades of economic integration and how far a country goes along this path determines what benefits they get. In order these steps are:
Free Trade Area - free trade in manufactured goods only as a rule
Customs Union - common external barriers with free trade inside the union
Common Market - Customs union plus freedom of movement for labour and capital within the Common Market
Economic and Monetary union - Common Market with one currency, eliminating the need for exchange rates
Political Union - One country
There are variations on these. The important point is that as countries allow greater integration they gain more benefits, but there are also some costs which include loss of domestic political control and in some cases the loss of the ability to pursue independent economic policy.
It would be useful to review the economic costs and benefits of EU membership now so that you can tell the political from the economics points that will be made in the next week or so.