How to Standardize a Manuscript to US or UK Spelling

Determining whether a book is written in US or British spelling can sometimes be difficult. Before editing a manuscript, you have to know first whether it is written either in US or British convention. 

 Here is how you do it: 

1.   Open the file using MS word. Once the file is open, check the status bar (located at the bottom of the page) for the language the file is set. But there are times that the file is set in US language where in fact the word consistency is in British spelling.
2.  Check for the word usage.  British spelling uses -ise, -isa-, and -isi- for some words although usage of -ize, -iza-, and -izi- is acceptable if the author has been consistent in the entire manuscript.

• US convention strictly uses -ize -iza-, and -izi-.   For example,characterise, characterisation, and characterising rather than characterize, characterization, and characterizing. 
• Usage of -or for US versus -our for British spelling. For example, colour, endeavour, and rigour instead of color, endeavor, and rigor. 
•  When the past tense, gerund, etc. is formed, the final single consonant is spelled double regardless of stress, for example, modelled, channelled, and labelled. While in US spelling, the final consonant is doubled only if the stress is in the final consonant, for example, preferred, occurring, etc.-t or -ed endings for the past tense of the verb. In British, use both forms of spelling, that is, spelled or spelt, while in US, -ed is the preferred form, for example, spelled. 
•  Use of -ce versus -se for some nouns. British spelling uses -ce for nouns like defence, licence, and practice, but -se for the verb forms of these nouns, for example, defense, license, and practise. US uses both forms for the same spelling, for example, practice (noun or verb) and license (noun or verb).
•  The suffix -wards is common in British, while -ward is more common in US spelling (e.g., toward vs. towards). Use of -re for UK, for example, centre and metre, while meter and center for US. Use of -ph- for UK, for example, sulphur, while sulfur in US.
•  Usage of ae for UK, for example, haematology, while US uses "e," for example, hematology. UK convention generally uses oe like in maneuovre and oedema, but US uses "e" like edema and maneuver. UK also uses -ogue, while US uses -og (analogue, analog). 
• There are other word spellings distinct only in British spelling, like artefact, grey, leucocyte, among others. Make sure to check the dictionary for the right spelling. After checking the word usage count it one by one.

3.   Serial comma or Oxford comma. US spelling uses serial comma. A serial comma is a comma placed at the last item of a series, although usage of serial comma or Oxford comma in British is now acceptable as long as the author has been consistent. For example, in the series: apples, oranges, and lemons. 

 4. Quotation marks. UK uses single quotes for emphasizing texts or to separate the quoted text, although the usage of double quotes is acceptable if the author is consistent. Note: The period and comma are placed right after the closing quotation mark. US spelling uses double quotes as standard. Periods and commas are placed before the closing quotation mark. 

 5. Check for i.e. and e.g. British spelling does not place or set off i.e. and e.g. in the sentence. The comma only comes before it, for example: I want to buy fruits, i.e. apples, oranges and lemons (note no comma is placed after i.e. The same applies for e.g. in UK), while in US usage, I want to buy fruits, i.e., apples, oranges, and lemons. But always set off that is and for example with pairing commas when used in the sentence.

 6. Author affiliation and background. There are times that you can not decide whether the author is using US or British spelling. Try to check the author's affiliation if he was born in the UK or USA, or born in the UK but raised in the USA. 

 7. Set the file in US or UK spelling. Once you have determined that the author is not using serial commas, consistent in using double quotes, and the number of words has been spelled in British spelling, set the file in UK convention. Click the language portion of the status bar, and set it to the correct spelling convention. 

 8. Start editing. If the file is now set in US/UK spelling, edit the words according to its convention. Use serial commas for US, retain if consistent in UK. Change single to double quotes if US, but retain double quotes in UK if consistent. Use a standard dictionary for your spelling. Merriam-Webster's Dictionary is preferable for US, while Oxford Dictionary in UK.

Note:  There are times that a style-sheet comes along with the manuscript. Make sure to check if the spelling has been specified. Check the dictionary for the variant spelling of some words. Some UK words are acceptable in Merriam-Webster, so do with Oxford Dictionary. You can use Merriam-Webster Learner's Dictionary if a word is chiefly a UK spelling or a variant form. Be careful in changing quotation marks in quoted texts

Source: http://www.wikihow.com/Standardize-a-Manuscript-in-US-or-British-Spelling
           http://www.scienceeditingexperts.com/uk-and-us-spelling