* You could decide which area of science you are most interested in. Are you more interested by the synthetic aspect of chemistry, or more by the characterisation part? Are you more interested by answering fundamental questions, or do you want your work to have potential applications quickly?
Once you have decided about a general subject (it can be anything, a few examples: magnetism frustration in glass phase, natural product synthesis, lithium-ion batteries, spectroscopic studies of lanthanide complexes, computational studies of enzyme active sites, semiconductor thin layer deposition, nanoparticules aggregation,... to name but a few. The choice is huge. Too big to get bored
), start reading as much literature as you can on that topic. Try to understand where the hot questions are, what need to be answered, what understanding is lacking.
* If you can't decide on a topic yet, you should read through a wide range of scientific publications to get an idea of what is going on. Perhaps, you'll come across an article that will catch your curiosity so much that you'll decide to keep working on it.
* Very important as well, you should decide how long your project should last. Are you on for a short term project (a few months)? Then, choose something simple that will give results quickly. If you can have your project running for a longer time (a few years), then you can go on for a more challenging task.
* Think about the equipment required to complete the task. Can you get access to it? If not, can you get in touch with someone who has it? There is no point starting a research project if you can't finish it because of lack of a particular equipment.
* Similarly, you should look at how much it is likely to cost. Except if you don't mind risking to go bankrupt.
Can you get more funding later on?
* What about your coworkers? Will you work alone, or with someone else?
When starting research, you'll realise that there is no teacher to give you questions, exercises, tests, answers and rankings anymore, as you are probably used to from school and university. Now, it is your task to ask questions to yourself and then answer them the best you can.
When reading a scientific paper, ask yourself: what can I do to go further than what is reported?
Try to understand the main idea of that paper: what are the authors trying to do, to tell?
Then, combine the knowledge you collected from several publications in order to produce something new. Add a touch of imagination and creativity into your ideas. This can transform a good, scientifically sound work into an outstanding one.
Finally, the most important of all my advices: have fun!