Erecting a tarp can be as easy or hard as you want to make it. In it's simplest form as either a ridge or lean- to it can be thrown up very quickly and if pitched with a little care and consideration to the conditions, should offer adequate shelter ... obviously, that depends on your understanding of adequate!
Even these simple tarp configurations will require something to support the material of the tarp though, trees, sticks, walls or your bike can all prove useful for the purpose - simple!
Last summer I found myself riding down through a small, high sided valley. It was starting to get dark and I was looking for a spot to set up camp. Flat ground was at a premium so the first bit I came across became the evenings spot. Obviously the first job was getting a brew on and the second was sticking my tarp up as the folk who know had promised heavy rain in the night. Did I use sticks? No there weren't any. Did I use trees? No trees, hence no sticks. So you used a wall or fence then? Nope, didn't have the option of either. In the end I took my front wheel out and used that to support one end and my upturned bike to support the other. So there I was sorted, I had shelter ... I also now had everything in my bags upside down so looking for stuff in the dark involved emptying everything out and losing it in the grass, fantastic!
122cm tarp pole ... erm nice!
I lay under my tarp, listening to the rain and thinking. My main thoughts were about finding something else to help hold my tarp up, something that I could pack easily, didn't weigh much and would actually be a benefit rather than an ill conceived burden ... the picture above shows my solution. This foldable aluminium pole is 122cm long, weighs 120g and folds down to 33cm, so it fits the criteria I mentioned above with regard to packing and weight ... but is it a help or hindrance?
Yes, I know I've used this pic before.
Well, I can safely say taking a pole along with a tarp makes a massive difference not only to where you can pitch but also to how you can pitch. With a little practice and thought your tarp can become much more than a basic ridge or lean-to. The big advantage with a pole is that it allows you to support the tarp from underneath and 'inside', so much more coverage is possible than if you only support it from the edges.
I got my pole from Ultralight Outdoor Gear, they are available in 3 different lengths, 90cm, 115cm and 122cm ... bear in mind that when packed, the 122cm pole is shorter than the 115cm one due to it folding into 4 sections rather than 3.