1.
Plan your time - I found this very useful as I had set myself mini deadline of when I wanted each sections to be done. This was helpful because it allowed me to know what I should be doing and when and that I made sure I made enough time to cover everything.
2.
Structure - I found planning out the structure of my dissertation helped by splitting it into sections and writing down what needed to go within each section as well as what the word count should be. I found this super helpful because when I went to write a section of the dissertation I can easily see what needs to be included and how many works I need to write, it meant I wasn't stressing about what I should be writing and I could make sure I was hitting all the key points I needed to.
3.
Speak to your dissertation tutor - not sure about your university but at mine my dissertation tutor was the one which marked my dissertation, so listen to what they say and what needs to be included because that's what they are going to want to see within your dissertation and they are telling you what is going to get you those marks. If you are unsure what marketing theory to use I would definitely recommend speaking to them as they can help and point you in the direction you need to go.
4.
Research - I am not sure how your planning on doing the data collection whether that's through questionnaires or something similar or getting your data from online but this is the section of my dissertation which took me the longest. I handed out questionnaires for mine and didn't realise how long it would take to get reponces from people and get what amount I needed, I would bare this in mind if you are doing the same and I would hand them out as soon as you can to get the most amount of responses.