Any organisation should have a core set of widely agreed-upon rules and basic principles. Usually, these rules and basic principles are written down.
For example, together you could write down the demands of your organisation. This way, it is clear to both your members and the outside world what your organisation stands for.
The following aspects are often included in the constitutions of activist organisations: principles, manifesto, rules, demands, organisational structure.
Define your aims (or goals/objectives). This will help guide everything the organisation does, including the structure, messaging and tactics. There is extensive accessible literature on goal-setting frameworks to use. For one example which is directly applicable to politics, and written by a former political communications strategist, see chapter 1 of Winners: and how they succeed by Alastair Campbell. Campbell sets out a framework he calls "OST" (objective, strategy, tactics), which has its merits in political organising regardless of Campbell's political leanings.
An organisation’s conditions can be thought of as its consistent and unwavering strategy. While these may be altered at some point, they are not to be changed regularly. Therefore, they are not to be confused with tactics, which are chosen under the guidance of conditions and are highly changeable. In this respect, the conditions help guide the choice of tactics. Once more, see chapter 1 of Winners: And How They Succeed by Alastair Campbell for a full discussion on how strategy relates to tactics, as well as goals. For an example of an activist organisation's conditions see the Core Principles and Values in Extinction Rebellion's "How to" Actions, Art, Logistics: towards the decentralisation of XR.