As a piece of advice, this may be obvious -- but to be successful get yourself a topic and area that you can carry out for quite a long time ---
A doctoral degree is not the end --- it could be if you want to just teach and only teach.  But otherwise, if you are interested in a research-oriented career, it should only be a beginning --
Where do you get a topic and an area --
Well, it depends on your area --
it may be in workshops like this one
it may be in normal course work
it may be suggested by a friendly mentor
or, read things like the new york times and look at some of the science writers --
benedict carey 
gina kolata
densie grady
-----------
Some examples:
Biomedical areas --
diet and the control of Type 2 diabetes
immunotherapy for treating cancer
Alzheimer's disease and infections
Psychology areas --
imaging techniques and the control of error rates
concussions and sports --
We will use this as an example --  google: concussions in sports research lab university
replication failures in psychology experiments
Quantitative areas --
handling "big data" generally
machine learning methods --  the importance of cross-validation
clinical areas --
the diagnosis and treatment of schizophrenia, autism, parkinson's, and so on
medical uses of marijuana
------------------------
If you can, when you apply for graduate study -- have a particular person in mind that you would want to work with --  we are all suckers for the attention
For example, if you are interwsted in eye-witness identification, consider Gary Wells at Iowa State
for false confessions, consider Saul Kassin at John Jay College of Criminal Justice and CUNY Graduate Center
Or, look at places like the Beckman Institutes at Caltech or Illinois --
Look at Illinois bookmark --
Cognitive Neuroscience Division
Behavioral Neuroscience Division
Look at Texas bookmark --
---------------------------------
How do you support your graduate study?
If you applied to Illinois, for example, admission comes with 6 years of guaranteed support -- as long as you are in good standing
You might be running subjects or being a TA --
Once there, you might also apply for a multi-year NSF fellowship
So, if you are doing the usual research oriented career, you shouldn't have to go completely "on your own nickel"
If you are looking for a medical degree, you are not as fortunate --
unless you do the National Health Service or the military
Or, get into an MD/PhD program somewhere --
At Illinois there are some campus-wide diversity fellowships available through the Graduate College -- many of these go for 2 or 3 years --
Keep in mind that many science-based careers expect some number of Post-Doctoral years before you get a real academic position.
-------------------------
Finally, there are three skill areas that I suggest you get experience in --
1)	Fluency in the statistical language called R -- free and open-source
Google r_class_material
2)	Fluency in the Matlab computational environment both for graphics and programming
Google matlab_presentation_2013.pdf
3)	Fluency in the Tex/Latex environment for the production of science-oriented manuscripts
Google latex_class_material
--------------------------
Finally, if all else fails, google: “manual_sci_evidence.pdf”
and get the Reference Manual on Scientific Evidence for free