This House, as a worker seeking to start a union at our workplace, THW choose the established, AFL-CIO affiliated union (UFCW, SEIU) for your industry rather than the independent union for your company (Trader Joes United, Starbucks Workers United).
Established, AFL-CIO affiliated unions (e.g. UFCW, SEIU) were usually founded to serve specific industries (for example, food and retail for UFCW and service industries for SEIU), but most have gone on to vastly expand the trades they are willing to represent workers in. They provide financial and professional assistance in securing the union initially (through an election or, rarely, employer acquiescence), bargaining for new contracts, and managing grievances and disciplinary procedures. Rank-and-file members pay dues partially to a local that focuses on their region, but often most go to the national or international union. Members also elect certain union representatives for local decisions, but higher level decisions are often ultimately made by union higher-ups, who are hired and promoted like any other job. (Although workers always vote directly about whether to accept a contract for their workplace or send the union back to the bargaining table). Independent unions for chain workplaces (e.g. Trader Joes United, Starbucks Workers United) have some collaboration and higher level coordination between different shops, but each unit is ultimately in charge of their own strategies and goals. All leadership is typically directly elected. All leadership and logistical roles are filled by workers, from initial organizing to union management. If dues are required, they go to serving the needs of the individual workplace.