To add to the above posts, I have had many of the same questions you did, and while I am only relatively new to Christianity and belief in God, I have found quite a few things that were shown to me by God to help me grow in Him.
One of the first and most significant ideas that came to me while thinking about the existence of God (and going along the same lines of the Creator as Light heated) was the idea of interior decoration, decoration in general, or landscaping. I have worked landscaping jobs as well as construction jobs, and always have been amazed by the differences that are within us all. Some people like a tree over here, some a garden over there. Some people would love a window here, or a nice stone walkway to the street on that side of the house, winding and curving in this specific way. I have heard too many times words along the lines of "No, I didn't want it there" or "I think it'll look better this way, lets try this idea out and see how it looks."
Yet never once have I heard anything along the lines of "That tree/flower/rock/bird is out of place" in a natural setting, such as a protected national/state forest. Never once have I heard "That waterfall should have never been carved into that specific spot, but should rather have come out over there." With that specific example, look at Niagara Falls, one of the "Wonders of the World." Never once have I heard that the falls are one of the worst designs ever made, or they could have been shaped/carved out of rock better if it had worked this way instead of that way.
Look at the chemistry of water also. I am remembering this from a very long time ago in intro-chem in high school, so I cannot even begin to give you the chemical facts of why this takes place, but even so, I don't think they would help totally explain the facts. Take any chemical composition or element (besides H2O), and put a solid form of it in a liquid form of the same element/composition. In every single case, the solid form would sink to the bottom. Water, however, is entirely different. Water, when frozen into a solid state of matter, creates a crystal matrix that creates enough pockets of air within the solid form, that it floats in its own liquid state.
Now, Imagine if this were not the case, and water acted like every other chemical element/composition out there, and its solid form sank in its liquid form. When lakes and ponds froze in winter, the ice would sink, displacing water from the bottom, keeping the liquid state on the top. This water would continually freeze into ice, and sink. Eventually, there would be no pond, there would be no water, except for the frozen solid forms of this water that had sunk and built up within the beds of the lakes/ponds. Now, imagine what problems this would cause for animals, plants and other creatures within these lakes/ponds. Without the ice floating on top of the water, creating a barrier between the air and the water and allowing these creatures to live, if instead the ice sank and displaced the water, building up from the bottom, these creatures would have to die, or "evolve" pretty fast in order to get out of the water, and survive on land in the frigid temperatures that were causing the water to freeze in the first place. Eventually, half the world would be out of fish. The fact that this does not happen, and water, the most abundant resource and chemical composition on our planet, floats in solid form instead of sinks, allows for life to continue to thrive and survive.
I don't think that could have come out of chance. Both the "external, natural" "order and design" of things outside, in nature, as they are naturally, without the help of man, as well as the incredible difference in one of our most needed and most significant chemical resources that allows us to survive and not perish through problems that would most likely eventually come about, are, to me, evidences of God, a Divine Creator. I cannot see either of these happening merely by chance.
We do not question the marvelousness of many natural occurrences, lightening, rain, wind, clouds, storms, even natural disasters. These things are all part of a cycle of renewal, growth, birth and death. The natural course of things within our world is just too complete, too flawless to have happened merely by chance. If I knew any more about sciences (I did not graduate as a science major), I could most likely look at so much more as wonders of a creator that had a plan, that was able to keep things so balanced throughout the world in such a way that the Earth would continue to thrive for millions of years without fear of disappearing, burning out, or collapsing from a miscalculation between everything.
You asked for signs from God stating his presence, and I personally believe that there are signs from Him all around us, we are just too busy in life to be able to recognize them. Even our own human intellect is a natural wonder of God, as was stated before.
I know this was probably not the most eloquent or Christian-based responses out there, but it is what helped me look at not only the world, but also the existence of God, a Divine Creator, in a whole new light, and one that has opened my eyes.
I hope this helps, if you need me to clarify or explain anything, I'll be happy to, just let me know.
