Write out the main concepts and underneath each concept add any synonyms or alternative terms.

Logic grid for a search on Gastroduodenal Motility and Type 2 Diabetes Mellitus
might begin like this

MeSH (Medical Subject Headings)
Use the MeSH database to find the subject headings PubMed uses to describe these concepts.

The subject heading has been in use since 1966.

Add gastrointestinal motility to the logic grid.
To ensure that PubMed searches only for the Subject Heading add [mh] after the term.

gastrointestinal motility[mh]

Now look at the Entry Terms.

You could also add gastrointestinal motilities, intestinal motility, and intestinal motilites to the logic grid.
Add [tiab] to these terms.
This will ensure that the terms are searched only in the titles and abstracts of citations.
It also ensures that the terms are searched as phrases, without [tiab] PubMed would search for

gastrointestinal AND motilites

Your first logic grid column should now be looking something like this

Scroll down the MeSH Database screen and view the MeSH Gastrointestinal Motility in the hierarchy of MeSH.
The more specific MeSH listed under Gastrointestinal Motility will automatically be included in a search for Gastrointestinal Motility.
It's worth considering searching these terms in titles and abstracts to find citations that don't (yet) have MeSH added to describe their content.

You can use * to truncate terms to reduce typing, but don't truncate MeSH or phrases.

clot* will find clot, clots, clotted, clotting, etc but will also find cloth, clothes, clothing

Now look at the next concept, Type 2 diabetes mellitus
Type this into the MeSH database

Add the MeSH to the second column of the logic grid, then look at the Entry Terms to see if there are any terms that authors might use in titles and abstracts of articles to describe the contents.

There are a lot of Entry Terms that you might add to the logic grid

You should use this grid to sort out the logic for your search.
Join the terms in each column using OR logic.
In PubMed the logic terms must be in capitals, OR AND NOT.
Enclose the terms joined by OR logic in a set of round brackets.

Join the sets of bracketed terms by AND logic.
The search from this logic grid becomes

(gastroduodenal motility[tiab] OR gastrointestinal motility[mh] OR intestinal motility[tiab] OR gastric emptying[tiab] OR gastrointestinal transit[tiab] OR migrating motor complex[tiab] OR migrating myoelectric complex[tiab] OR peristals*[tiab]) AND (type 2 diabetes[tiab] OR diabetes mellitus, type 2[mh] OR adult onset diabetes[tiab] OR ketosis resistant diabetes[tiab] OR maturity onset diabetes mellitus[tiab] OR niddm[tiab] OR mody[tiab] OR non insulin dependent diabetes mellitus[tiab])

This can be entered into the PubMed search box.

When You Can't Find a MeSH
Sometimes your search for a MeSH can fail.

When this happens it's often useful to search for your term in the titles of articles.

Change the Display format to Citation.
This format includes the MeSH.

Make sure you check several of the citations for consistency.
In the example above a combination of two MeSH Receptors, Androgen ANDed with Signal Transduction would probably cover the concept.
You'd find more citations if you searched using the North American spelling signaling.

Related Articles
PubMed uses a weighted algorithm based on title words, abstract words, and MeSH to find other articles in PubMed that are similar to those you have already found.

Click on the Related Articles link to the right of a PubMed citation.

Study Types
Evidence based studies require the use of particular study types for determining best evidence.
Here is a link to PubMed searches on several study types that might be useful.
Run the study type search then AND your search terms.

Study Types

Major MeSH
Using Major MeSH for one or more term can help you to focus your search to the most relevant articles.

example search asthma AND child

In the MeSH database find the first of your search terms.

Scroll down to where you can restrict your search to Major MeSH and click in the box to the left.
A tick will appear.

Click on Sent to and then on Search Box with AND

Repeat with the second MeSH child.
Click on the Search PubMed button.

Limit Searches Using MeSH Subheadings
Example search

androgen antagonist therapy for prostate cancer

Find the first MeSH androgen antagonists.
Scroll down to the Subheadings and click in the box to the left of any subheadings you want to search.
You can click in more than one subheading and PubMed will OR the searches.

Click on Send to
Then on Search Box with AND

The software begins setting up a search to run in PubMed.

Now type in your second concept term prostate cancer.
Click on Go.

PubMed redirects from this term to the MeSH Prostatic Neoplasms.
Click on the link for the MeSH.

Click in the box to the left of the MeSH.
Click on Send to.
Click on Search Box with AND.

Click on the Search PubMed button to run the search in the PubMed database.

Limiting Using PubMed Clinical Queries Filter
Click on Clinical Queries in the blue left hand sidebar in the PubMed Database.

PubMed Limits
You can limit the number of citations you find, but you must be aware that you could lose important articles.

You can limit by date