One of the main problems faced by conlangers everywhere is an inability to fill out a lexicon. They are difficult things to do, but done in a systematic way, they become a snap. Here are some pointers on how to achieve said approach:
- Firstly assess your conlangs setting and theme. Was it originally, or is it still spoken by a religious culture? Is it a modern Auxillery language? Is it a language of magic? Once you have this sorted it will all be a lot easier.
- With the concept in hand, flesh out the basis for it first. In the first example, you should figure out some of the religion it came from, including a few myths from said religion (if you are using a real world religion, read up on it, specifically the religion's holy text). In the second look at the languages you are trying to branch. In the third figure out your magic system; does it require certain reagents to work? Is it based on a spiritual aspect or a level of meta-physics?
- Once these basis' have been developed, you can then draw words from these. For instance, in a language I mapped out loosely for a race of amphibious nomads, their word for "Hello" actually translated to "Which bend has led you here?" as the religion they were based around was heavy on the concept of regret, bad choices, shame and redemption. They believed that the god of Rivers was also the God of Returning Home (the river meets the ocean, and the word 'bend' is based on the word 'river' as is the words 'road' and 'snake'). So you should make a list of concepts from your basis and turn them into word roots.
- Then, you simply have to draw from your basis and combine roots accordingly. In my current conlang the name of it (Venlshëi) comes from a combination of the roots "wolf" "speak" "woman" and "all". The wolf is the symbol of the gods and the gods will, and in the mythology it was a woman who gave the people language.
- This should supply you with many words, and when you encounter a word you haven't yet made, do not make a new root straight away, but instead look at your current roots and consider if any could be used to make the word you need. If they cannot (and be sensible here, you don't want to make every concept fit with a single root) make a new root, and see what new words you can make.
I hope I helped, and if you have any questions or anything to add please do tell me.