Basics!

Ingredients

If you are making things up as you go along, think of the characteristics of food that you like, and why, and concoct variants. Sometimes you're missing ingredients in a recipe; don't be afraid to try substituting similar things!

This might help: https://myrelationshipisedible.files.wordpress.com/2012/10/chart.jpg

Generally when creating a dish you are aiming for a taste and texture balance that remains interesting; but avoids putting clashing flavours together, or overdoing things by adding too many flavours.

Seasoning

Different people have different preferences, but most people agree that gruel without any taste at all is not palatable. Some seasonings are activated by heating them, either on its own, or with some oil, whilst others are best used fresh.

Good list of what is what: https://www.thekitchn.com/quick-guide-to-every-herb-and-spice-in-the-cupboard-108770

Smol tips in this area

1. Taste your cooking as you go, so you can adjust it.
2. Take in to consideration the strength of flavour of the other ingredients that you are using before adding spices.
3. If you've put too much vinegar or salt, adding a bit of sugar fixes it, and vice versa (to a degree). If you've added too much sugar in a dessert, sometimes adding a bit of lemon helps.
4. If you've overflavoured something, add more bland ingredients. Nuts, chia seeds, couscous, potatoes, aubergines, cottage cheese, paneer, tofu are all good options to tone things down a notch.
5. Pre-marinating things is important for stodgy food that might need time to absorb the flavour, failing to do this might result in an uneven cook. A good rule of thumb is 4 hours for most meat and root vegetables and 1 hour for fish. There seldom are reasons to marinate fresh / leafy vegetables. 
6. Little garnishes like fried onions, spring onions, parsley, chilli flakes, ginger oil are simple little things that you can add at the end to spice up your cooking.

Order of work

Main rules

1. You tend to add anything that you want to permeate flavour wise right at the beginning, unless they are things that are easily burnt (like sesame oil)
2. If things are canned, it is likely that it is soft enough to be added at the end, unless you are using it to impart flavour on your dish

Different things cook at different pace

Harder, stodgier things tend to cook slower, wherelse softer, crunchier things tends to cook fast. What you want to do when planning out your cooking is to end up with all the different ingredients at the texture level you want. This is particularly important when you are using many different ingredients in the same dish; because messing up the order of work can result in some pretty horrendous results. Before cooking, it might be worth grouping together the ingredients which have similar cooking rates.

Most of the time you'd be looking to finish cooking most dishes within a few minutes of each other so one dish is not at a significant temperature difference than another, unless you're in to cold dishes of course ;¬)

Different strengths of fire

1. Choose high heat if you are looking to sear things or have different textures within a particular ingredient or are  flash cooking things
2. Choose lower heat if you want a consistent texture / slow cooking things for a longer period of time

A general rule of thumb is as follows:

1. Start part-cooking any ingredient that needs to be cooked slightly to be used in a recipe, or takes a long time (e.g. rice, potatoes)   
2. Heat oil/butter/other 'lubricating activator' up until bubbling, then add spices / salt and cook until aromas are released / nearly golden (skip if boiling)
3. If you are using this to marinate, leave to cool slightly, then pour over desired ingredient(s). If you are cooking straight; add other ingredients in the order in which you have determined as per above. 

A scale of common ingredients and how quickly they cook

First	Onions / garlic / Leeks (flavour / soft)
	Potatoes
	Suede
	Parsnips (soft)
	Carrots (soft)
	Parsnips (crunchy)
	Leeks (soft)
	Aubergines / Brinjal
	Apples (soft)
	Carrots (crunchy)
	Leeks (crunchy)
	Lettuce (soft)
	Celery (crunchy)
	Spinach (soft)
	Tomatoes (retaining shape)
Last	Apples (crunchy)