Cooker opposite Sink
The idea that this causes a problem stems from the days of cookers containing open fires (Fire Element) being opposite sinks (Water Element). This gives a clash between the two elements leading to friction and arguments in that area of the house.
In modern kitchens where the “Fire” is only on whilst you're cooking and for the most part is completely sealed inside the cooker, it doesn't seem to be much problem. But if you find that it is in your house, and want to fix it, put some Wood element between the sink and the cooker. You'll probably find that the most effective way of doing this is to use Green, rather than objects made from wood (they tend to have lost most of their “Wood” Element by the time the trees from which they are made have been cut down for a couple of years).
Now lets look at some of the more common “enhancements”
Money plant in SE for wealth
Based on a PaKua analysis the southeast is a wealth influence (there's also another more powerful wealth influence in this area as well until 2016). You can strengthen and tap into both by placing one or three Money plants there.
Pair of “whatever's” in SW for relationship
Again based on the Pakua the southwest contains one of the relationship influences. You can tap into this by placing a pair of things here – red roses or Mandarin ducks are the usual choices. If your pair of objects are either Fire or Earth elements, so much the better.
Whilst we're on the subject of relationships, remember the symbolism regarding the number of things you use – I've seen single people with single unpaired objects in several relationship areas in their house and I’ve seen them meet partners when they replaced those with pairs of objects. But remember that more that two identical objects in a relationship area can also create problems!
Metal in North for Career
If you put Metal Element in the north, it will usually have a mildly beneficial influence on career.
A lot is written about keeping the loo seat lid down, shutting the bathroom door etc.
That is fine if the loo is draining water out of the building where you don't want it drained out.
But that's not always the case. Once you start to look a bit deeper with some of the more advanced water placement formulas, you will find that there are places where it’s beneficial to have water draining out of a building. If your loo happens to be in one of those, you need to keep the loo seat lid open to encourage the drain (closing it in that situation is likely to adversely affect your finances). You can also do some more advanced things with water. In my own house for instance I've paired a loo which drains water where it is beneficial to drain it with a water feature stimulating the energy in another part of the house where it’s beneficial to bring water in, to very good effect.
However if your bank account is suffering, the loo might be one of the culprits. In this case keeping the seat lid closed when not in use will help. You can also put some Wood Element, next to the loo (a vibrant leafy plant is ideal if there is room for it). The Wood Element weakens the Water Element, and the upwards movement of energy in the plant helps draw the energy up away from the loo (so a “fake” plant no matter how nice and realistic it looks won’t do the job nearly so well).