A successful crowdfunding campaign is one that encourages its supporters to become involved with the cause, and keeps them engaged once it is finished. A very effective way of doing this is to offer them a reward relevant to the campaign, in exchange for their contribution. 
Whilst your backers will feel more valued and appreciated when their support is recognised with a reward, a campaign with an incentive scheme typically also attracts a far larger audience of potential backers than one without.
The key here is to know your target audience, select the most appealing reward for them, and showcase your perks to their best advantage in your campaign content.
What kind of rewards can be offered?
Although the only limit to the rewards offered need be your budget and imagination, it is nonetheless advisable to be sensible, to ensure the incentives are proportionate to the amount contributed, and are something you ultimately will be able to follow through with, long term.
Goods or Products 
If you are lucky enough to gain a corporate partner or sponsorship for your crowdfunding campaign, then that business may have some applicable goods that you could offer your potential backers, such as stickers, posters, magnets, merchandise or even shopping vouchers, depending on the industry.
Digital Rewards
Don’t underestimate the power of the online reward, such as ‘thank you’ emails, shout-outs on social media or digital downloads. As these perks generally cost only your time and effort, they are especially suitable for a campaign with no spare cash to spend on rewards.
Experience Rewards 
If you have limited reach when it comes to tangible rewards or online presence, then you might instead have a sellable skill to offer via workshops or creative collaborations, or could lead behind-the-scenes days, or provide tickets to applicable events. Make your backers insiders to your creative process and the project development, and let them feel part of it with visits to the office, coffee mornings, or even just a phone call.
Campaign Exclusive Rewards
To really make your backers feel special, you could offer something that will not be available following the close of your crowdfunding campaign. For example, a discount or pre-order on a relevant product may entice more support, whilst sharing a secret or exclusive piece of information, or adding contributor names onto the final product, are also effective incentives.