My short answer is to mostly do nothing. I grew up with parents who were not creative at all. I can remember my mother being very unsure what to do to encourage my obvious creativity. What she did do was perfect though. Firstly she allowed me to be bored. Her favourite saying on the topic was "Only boring people get bored". She left me to my own devices 90% of the time. I lived outside when the weather was good, making forts, roaming in the bush with my dog, creating imaginary worlds in my head. When the weather was bad I had to make my own fun up inside. When I was creating she never discouraged me or told me I couldn't do something but she was very hands off. She made sure I had glue, paper and crayons or pencils (there really wasn't the huge variety of art materials that is now available for children) and of course she praised the results of my makings.
This combination of freedom, boredom and limited choices of art materials feed my creativity. She didn't help me but what she did was instil in me a faith that I could achieve anything I wanted, nurturing my independence and teaching me to be capable.
I think a creative child will be creative no matter what and as a parent you just have to stand back and give them the freedom to do so. For me creativity is a force that runs through my life. I couldn't stop being creative just as I couldn't stop breathing.
That being said there are some things you can do that will help to nurture an environment where your child can be creative.
1. Make some boxes up of bits and pieces that can be used to make things. You don't need to go and buy a whole lot of stuff. Things like pens, paper, old bits of cardboard and containers that would normally go in the recycling, scraps of materials, old magazines or books they can cut up, scissors, tape, glue, a stapler, wool, string, anything odd thing really. My father's empty cigarette packets was my favourite art material and my son adored a roll of masking tape and some old boxes.
2. Turn of the TV, iPad, computer, playstation etc. Allow them to be bored and don't step in to fill up the gap when they are. Don't tell them what to do other than maybe point them towards the boxes you've made up. I know this can be painful as a parent having to listen to the 'I'm bored" whining but when they start to realise you're not going to do anything about it they'll make up something to do. If the weather is nice you can use the line I used on my kids to get them outside (where nature is the ultimate playground for creativity). I'd tell them they had a choice, they could stay in and clean their rooms or they could go outside and play. Worked a treat.
3. Don't think they have to do traditional art to grow their creativity. Being creative can come in all forms such as imaginary games, constructing a fort, gardening, building a sandcastle, making up songs in your head or flying paper planes.
4. Let them solve their own problems. You can facilitate this by asking them how they think they could fix the problem and if they are stuck tell them different possibilities. Kids are clever and can often come up with their own solutions. Creativity is all about problem solving.
5. When they have created something don't tell them they've done it wrong! Don't tell them their drawing is out of proportion or the perspective is not right or the sky shouldn't be red. They will get hung up on perfection in their creations soon enough. Telling them they haven't done something right will make them feel that they are no good and then they'll stop creating. Plus mistakes as an artist can be your greatest source of inspiration and show you a new way of doing something. The only exception to this is if they want more knowledge such as wanting to understand perspective. Then help them find or better yet show them where they can find the information themselves.
6. Let them daydreaming. It is necessary for creativity. I think we expect our kids to be doing something all the time but doing nothing sometimes is ok. I spent a huge amount of time in my head as child, daydreaming. From the outside It would have looked like I was being lazy but inside my head whole worlds were being created. I still love daydreaming and will often drift off when my husband and I are out. He reads and I daydream.
7. If you're wondering how to develop their skills let them explore without pressure whatever it is they love doing. It needs to fun for them. By exploring without realising it they will be practising and will develop their skills. Give them a physical space to do this and a mental space, as in time away from "have to's" like homework and scheduled activities.
8. Let them copy from other artists. This is a great way to up your skill level and learn what you do and don't like. As Pablo Picasso said "Good artist's copy, great artists steal". Get books about art from the library (or any other topic that interests them), take them to art galleries, stop and look a graffiti on the streets, notice beautiful graphic design, or just sit quietly and watch the sunset. All these activities will open there eyes to seeing.
Pablo Picasso also said "Every child is an artist. The problem is how to remain an artist's once we grow up". I hope this post is helpful. Do you have any other suggestions ? If you would like some ideas of things to make here's a link to a great website of creative activities for kids