Traditionally, to invoke the energies of a planet or to make contact with spirits of that sphere, it is necessary to know where in the sky in relation to you that planet can be found at the time of the working. The Hexagram is the symbol most often used for planetary invocation. There are other methods for invocation which work just as well and for slightly different purposes. The Heptagram Planetary Ritual presented here was adapted from a working by Ben Rowe. It functions similarly to some other Sumarian/Necronomian styles of planetary working, but does so in a more balanced and reliable manner. I personally don't feel that it is necessary to know where in the sky a planet is at the time of the working. I do agree that it would add to the number of correspondences in the physical realm and be in greater harmony with the universe in a sense, but if you already have a connection or link with a particular planet (which you certainly do having been influenced by them all throughout your life/lives), then it is still possible to invoke those energies or speak with the beings from around those spheres even though you might be sitting in a chair facing any random direction at the time. As with everything else in Magick, if you believe that something is necessary, then it often becomes so. Your intent is usually the most important factor for initial success. I know that it is possible to invoke a planet's energies by sitting in one spot without a ritual; I believed it was possible and I did it as a result. If you've studied the basic concepts behind the rituals and why they work, then you should be able to (later) develop a think-it-and-do-it method of your own for working with the energies and spirits of those areas. Keep in mind that some rituals are still necessary when working with certain beings and they are not to be neglected or you will not have a successful working with them.
Basic Outline for invoking/banishing a planet the traditional way
1. Trace appropriate star (Hexgram or Heptagram depending on your purpose) to invoke or banish a particular Planet. Use a wand according to your personal system and the attributions of the wand, or the thumb (thumb traditionally corresponds to Spirit).
2. Vibrate the Divine Name (Hebrew Name of God) associated with that Planet.
3. Trace Sigil of the Planet in the center of the star (from #1).
4. Vibrate Hebrew name of the Planet.
5. Use appropriate Portal Sign (Rending to Invoke, Closing to Banish).
6. Perform whatever working you need to perform at this point- have conversation with spirits, learn, or charge a talisman etc. Use some formality here if you're dealing with new entities (especially the Planets- formally introduce yourself and state your purpose or request and be respectful).
7. When finished, banish the planetary energies by using appropriate Hexagrams or Heptagrams, and use Closing of the Veil etc. Don't banish over or near a talisman that you have just charged as that will undo what you've just done!
This is only the standard way to do things within the Hebrew systems of Magick. There are other texts you can study to get more ideas, such as the Greater Key of Solomon the King. Your own personal astral and Enochian/Angelic work will also yield substantial results.