Very active and eager, I appreciate such spirit.

I suggest you look at Cochrane Handbook which is freely available here:

http://handbook.cochrane.org/

This can answer most of your questions about systematic review of RCTs. Also, I suggest you to start writing your protocol/proposal on your topic of interest supervised by a researcher who's done at least one systematic review of RCTs. If you could define your research question in a clear and answerable way, the rest will be following the handbook. Actually it is your question that tells you what should be included and what should be excluded. Feel free to ask more questions if you couldn't find the answers. Good Luck

http://handbook.cochrane.org/

I would also suggest looking over a document provided by the Centre for Reviews and Dissemination (http://www.york.ac.uk/inst/crd/pdf/Systematic_Reviews.pdf) as it provides a nice overview of many of the questions you will run into when performing your systematic review.

Generally though, you're inclusion criteria is reflective of your 'question', or what you're trying to answer with your systematic review. The inclusion/exclusion criteria helps ensure that your question is focused, and prevents bias from selection of studies as the criteria are defined before your literature search, and before you begin including/excluding studies.

An example reason why you would choose to include/exclude a certain age or gender: You're interested in type 2 diabetes and the prevalence of insulin resistance in obese adults (please note, this is completely a made up question) -- therefore, it would make sense that you would exclude studies that reported on pediatric populations, especially because it is more likely that this population could have type 1 diabetes, and perhaps there is a reduced likelihood that younger age groups would have a greater prevalence of insulin resistance, which would underestimate your prevalence estimates.

Thank you Farhad and Jon for your precious time!

It depends on your questions. If you have a specific question for a specific population, your inclusion criteria needs to be specific.

Obviously, you need to first think on your research question and hypothesis. Then ask yourself, what do I need to get in order to satisfy my research problem? What are unnecessary data to exclude? From there, go. Good Luck 

If you are looking for a book , I would suggest : Meta-Study of Qualitative Health Research.

A Practical Guide to Meta-Analysis and Meta-Synthesis

Your exclusion and inclusion criteria should follow the focus of your research question. When you have a research question, try to be very specific. For example, if you want to know how a certain treatment is for cancer. Then you want to start asking, what kind of cancer? If let's say cervical cancer, do you do want to study all ages? Or you're interested to know specific ages that have the least or most effect from the treatment and so forth. By defining the parameters of your research question, you will know what exactly should be included or excluded. Then when it comes to the actual papers to include or exclude, you would start looking for articles that make sense to your research. If an article is written in other language that I have no clue about, then that would also be a basis for which it is excluded and so forth. Hope this helps alittle.

Certainly both Cochrane handbook and the University of York resources suggested previously are very useful. On a more practical point of view, I would say the inclusion and exclusion criteria are mostly defined by two things - your research question (what are you trying to find out) and the resources you have in your disposition to conduct the systematic review. For instance if you have a limited team and your literature search has yielded a great amount of papers you may want to restrict the time frame of your search to the past 10 years, or if you don't have someone in your team that speaks another language and can translate studies for you, you may want to restrict the studies to the ones written in English. In terms of the question you are trying to answer with the review,  i use the PICO (Participants, Intervention, Comparators and measured Outcomes) to define my inclusion/exclusion criteria. I hope this helps.  

be target oriented.  Systematic reviews can be very extensive, so it is easy to overlook or miss some important data.

 In pregnancy related systematic reviews, things get more complicated, and obstetric and gynecological history should be included along with other confounding factors..

Above there are some very good references. 

Thank you. 

http://www.elrha.org/r2hc/research/humanitarian-health-evidence-review/methods/systematic-literature-review-health-topics/inclusionexclusion-criteria/

As a quick answer I suggest you to use PICOTS Criteria for your inclusion/exclusion criteria.

Good luck!

The theory/theoretical framework you use for your analysis will also determine the scope your systematic review. A question can be answered by utilizing multiple theories -- the core of your systematic review should be linked to the main theories you consider to be most relevant to the question you seek to answer. Hope this helps.

It is imperative to first understand that, the theoretical framework that one uses for analysis will also determine the scope of your systematic review, hence the question can be answered by making use of multiple theories. It is for this reason that the core systematic review should be linked to the main theories that you consider to be the most relevant to the question that you seek to answer.

By and large, however, you're inclusion rules are intelligent of your 'question', or what you're attempting to reply with your deliberate survey. The inclusion/exclusion rules guarantees that your inquiry is engaged, and keeps predisposition from the choice of studies as the models are characterized before your writing search, and before you start including/barring examines

The key characteristics of the target population that the researchers will employ to address their study topic are referred to as inclusion criteria. Typical inclusion criteria include factors related to geography, clinical settings, and demographics.