(1) justify the approach you have taken
(2) explain in detail how the primary research took place
(1) Justifying the approach
If you think about your research topic - you can (in theory) undertake any kind of research - but will need to find the most appropriate methodological approach that fits the investigation you are undertaking. I use the image of an upside down tree trunk - with the sub-dividing root system as a visual metaphor. Often it is easy to jump to a choice of methods (questionnaire, interview, focus group), but it is important to justify why this was a good choice, what are its strengths, how can you mitigate (over come) some of the weaknesses. (For every strength, there is a weakness...)
Thus - the first choice is between qualitative or quantitative methods and then within each of these you will find a variety of approaches and then sometimes within these further options.
What I recommend is that you spend 3 hours in the library in the research methods text section and pull down 15 different texts and use them to construct a well referenced argument that uses the expert opinions of research methods authors to demonstrate a rationale behind your choice of methods. The methods section of an academic journal that uses a similar approach might be a good place to get a feel for the different kind of language that is expected.
Do not forget to cover mitigation, actions taken to anticipate or compensate for possible short comings in the approach. In the business world flagging weaknesses might not be common practice, but in academia recognising shortcomings preempts criticism for not having considered the issue and demonstrates the ability to self-critique, which is often seen as a virtue. Three modest items here should be sufficient. Anything too important may invalidate your research (disaster), and too many small points will detract the readers focus.
Suggesting that a certain approach is "quick and easy" will not engender the correct feelings in a markers mind, thus you may want to consider using phraseology that suggests "beyond the reasonable scope of a under/post graduate dissertation project" to cover approaches that might be too expensive, too time consuming, or just too big. Access to experts or research scenarios made possible by work, family or social networks should be openly discussed, but avoid positioning the research negatively e.g. "My dad took me to his work one day and I have a few chats with his colleagues" or "I watched people whilst I was working". Careful use of rationales, how the interviews were set up, how observation bias was avoided, how observations were recorded can impart credibility to such types of approach. Establishing the credibility or appropriateness of the research subjects is also achieved here.
(2) Detailed methodological description
You may remember cooking classes from school, or perhaps at home, most of us can use recipes. Part of the scientific approach of peer-reviewed academic research requires sufficient detail to be given to allow other researchers to follow on, perhaps trying to exactly replicate the study (think of pioneering heart surgery or nuclear fission) and validate the findings. Thus, sufficient detail should be given to allow someone to do this. Back to the recipe idea, this gives specific, detailed lists of actions in a structured order that allows repeated perfect cake baking.
Two medium eggs
Flour (any, but self-raising makes for lighter pancakes)
Milk (semi-skimmed or full fat for taste, lower fat for health)
Butter or fat for frying (avoid margarine, it tends to burn in the pan)
Serve with granulated sugar and lemon juice
Step 1: Weigh eggs, use same weight of flour and milk (a traditional balancing scales is great here)
Step 2: Put the flour into a mixing bowl, crack open the eggs and add them followed by the milk
Step 3: Use a mixer or hand blender to combine the liquid until a smooth, creamy paste is formed, with all traces of egg and flour gone.
Step 4: Melt some butter in a large frying pan on full heat and use a small cup to pour enough mixture into the pan to cover it all over.
Step 5: Check the underside of the pancake to see how well cooked it is (usually the top goes nearly solid). You are aiming for a golden brown colour patchwork.
Step 6: Using a sudden-lifting-jolting action from the wrist, in plenty of space, flip the pancake out of the pan and catch it again having inverted it. (Alternatively it is possible to turn over the pancake using a wide, flat utensil such as a spatula). Take care to clear up any spillages.
Step 7: When both sides are browned, serve on a plate with sugar and lemon juice.
You will note from the simple example above there is quite a bit of jargon (sometimes explained e.g. spatula), some ideas are quite difficult to express (I struggled with "flip the pancake") and clearly from the above I could have written more (nothing about clearing away or how to use a weighing machine), equally it could have been possible to write even less, but this would then have left the novice cook perhaps struggling to follow.
You probably need to avoid the formulaic 'step 1, 2, 3...', use full sentences and provide as much detail as possible, but ensure your writing is very tight or concise. This section may use few or limited in text references.
Where a pilot approach is used, highlighting changes made to the approach is helpful. If a questionnaire is used, include a copy in the appendix and reference it here. If problems with the methods were encountered that were not overcome, briefly mention it here and also flag this as an opportunity for further, refined research and as a limitation to the findings in the results. Some open criticism here actually can improve the quality of the work, but do not go overboard.
A careful blend of the two essential components listed above should see a solid methodology emerge. Key tip: reading other authors methodologies will help this make more sense and give you appropriate insights into accepted terminology and writing style.