1. Basic material rivalry: Do not try to advance at the same time with two professions that both need the same basic material. Jewellers, armour and weapon smiths come to mind, as they use a great amount of copper ore in the beginning (after Lvl 75 jewellers can switch to silver, the smiths will compete for iron).
Solution: If you want to avoid that problem, do not take two of those, but a profession that needs wood and leather perhaps, too.
2. Storage of refined materials: Basic materials can be stored in the bank tab (including precious stones now), but refined and advanced materials have to be kept in the regular storage tab. This means e.g. you can keep copper ore and bronze ingots, but not copper settings or adorned pebbles. This is an even bigger problem for cooks, that have a lot of refined ingredients (like cookie dough etc.)
Solution: Use, sell or give away. I can not say if selling extras you made for e.g. recipe discovery will result in a profit in the future - it was not the case during the 2nd BWE, were the demand on the most basic stuff let to strange prices at the BLTC market.
3. Character Level vs. Crafting Level: Basic crated items start with a level requirement of 10 and will advance in steps of 5 or 10. This can mean, that you are able to craft items you won't be able to use, like in my case, when my jewellery skills allowed me to craft fancy stuff up to level 20, which I had not reached on my Guardian, who was only lvl 17 in the end.
Solution: Craft for friends! In this option lies a great potential for intra-guild/friends list cooperation. Know a few people that cover other crafting professions, know their levels & demands and help out each other. If this works properly, you can outfit yourself quickly with 8 slot bags/boxes and jewellery, just by passing along copper ore and receiving rings & boxes in return.