It is very easy to get rather caught up in the timing of a spell. Timing is another tool that can assist you in your focus, however as always the most important tool in magick is your Intention, your Focus, and your Need and/or Will, the rest are just additional tools we use to help 'smooth' the path of the energy we are directing.
There are several aspects in magical timing the most well know and in my opinion most useful is of course the Moon.
Waxing (growing larger) it is a time for magick that focuses on increase and growth, Waning (growing smaller) time for decrease, neutralization and dissolution of energies, entities and habits.
The phases of the moon are also connected to the different aspect of the Goddess, as is different times in the suns path are associated with the different aspects of the God.
Dark Moon (Hag, Underworld)
This is a good time for inner working and gaining knowledge about oneself. Or, workings that confront self destructive patterns and fears. Not particularly a time for Magic per sea as for 'journey' work and meditation.
New Moon (Maiden)
This is the time of new beginnings new projects that focus on 'maturing' or 'growing'
Waxing Crescent (Mother)
This is the time of nurturance and growth, the time that you would ‘feed’ your hex signs, spells, sigils’, bindrunes etc.
Full Moon (Crone)
The time of wisdom and completion, this is the time that you would ‘celebrate’ the success of a project or the completion of your working. Also it is a good time to connect with your inner strengths gifts and enhance your knowledge, wisdom and skill.
The waning moon times alternate between the Crone and the Hag aspect of the goddess, depending mostly on the day and the planetary hour you are working in.
These are just generalities, different traditions have different interpretations, for example in Slavic Sorcery and Shamanism the moon is actually considered to be ‘masculine’ and the Sun is assigned with Feminine energies. Best way to find your own rhythm is to spend the time in ritual and ‘find’ your own particular timing and cycles, which can also be very useful in your day to day life. You may find you are more sensitive to certain types of energies during certain phases of the moon, or have prophetic dreams during certain phases. Find your own rhythm and cycle.
Next timing tool would be days of the week and planetary hours.