Fundamentally, partnerships only work with the right partners. Who is the right partner? Only you can decide, but some things to think about include:
Trust: you will depend on your partner. Is that trust well-placed? Check out Stephen Covey's classic book to get this foundation right
Knows your customer: for marketing, the partner should already have a strong customer base with your target. If they don't, then this partner is probably not the right one to help you reach customers better (but could be another type of partner, like development or supplier)
Win-win only: the value proposition for both you and your partner needs to be solid. If value isn't created and evenly distributed, then don't pursue the partnership.
Of course, there are many types of partnerships. To get you started thinking, here's a few types:
Affiliate marketing: in this structure, an affiliate brings leads to your business and earns a commission. Make sure you base that commission on the right metrics for your business bottom line. There are a lot of options (ClickBank, White Shark Media) in this space, and you can get started learning here or here.
Re-seller and distributors: these partners would sell your products directly to the end customers, and typically receive discounted pricing or a commission for their marketing and support services. In these cases, the manufacturer typically has a relationship only with the reseller, and not directly with the end customer. To set these up, you will typically need legal support and an agreement to ensure expectations are aligned.
Contractual relationships: sometimes, you will need to collaborate with a partner to combine services and give the customer the full experience they need. In some cases you could be the sub-contractor, working directly with a partner who coordinates the relationship with the end customer. This works well when you don't know the end customer very well, and can help you grow into a new segment or customer base. The key to is to collaborate effectively with the partners who you could join forces with, and set up a contractual agreement with legal support.