These are simply a few suggestions to improve one's ritual effectiveness.
1) The ritual itself needs to be meaningful. Every element should be a point of meditation for a period of at least a few days before the ritual is attempted, especially for the beginner and intermediary worker. The ritual architecture should be broken down and each point, from candles and their color and position in the ritual, to phases of moon or planetary positions or hours of the day, and each element should be a point of meditation until it comes alive for the crafter.
2) The energy of all the ritual implements should be reinforced and purified. Implements already sanctified should be cleansed of lingering energies and recharged, while other implements should be charded at least a day in advance. That way when you begin your spell everything is buzzing.
3) Some form of energy raising method should be practiced that works for the crafter well already. It is best not to go into this blind, but to be accustomed to raising, channeling and releasing energy as a matter of course.
4) In any ritual the statement of intent through the actual spell structure is the backbone. Everything else is supportive of that. Reinforcing this aspect of the ritual increases probabilities of success manifold. My suggestion is to craft your own spells. Write down the intent in plane english and with as much elaboration as you want. Do this a few days in advance so you have time to mull the spell over. Then in a relaxed frame of mind try to summarize the intent. If you have a ten line paragraph with a commentary explaining what you want in detail, intend the commentary fuse into the main paragraph and get a clean sheet of paper and write the paragraph over.
Then summarize the paragraph into something like four to six lines intending the original one be fused into the second version. Re-write that on a clean sheet as your new reference point. Now you need to convert the prose into poetry. Rhyming is good, but what matters most is poetic rhythm. Try to get four lines if you are a beginner to concentrate more force into fewer words.
Spellcrafters often wonder about spells bringing about what you say instead of what you mean. You need to search within if you hold even a tiny vestige of doubt surrounding this issue. You need to affirm that the words are a vehicle of your intent and meaning, and carry it. They are not the actual manifesting structure of the meaning itself, however. If you have moral misgivings, these may be valid, or they may be personal blocks of guild or the result of being blamed or judged in your life. It may take some soul searching, but at least to an extent such doubts need to be cleared. What you don't want is a subtext of unresolved issues polluting your spell. If such a thing is persistant, focus your spells on inner purification and psychic healing before you try to deal with material issues.
5)When all is in order, you should have a little poem. On the day of the spell, find some time to recite this poem a few times. Announce the words slowly and with passion, and in such a way that you feel your body vibrating with the tones of each letter and syllable. Recide in sing-song fashion. This is all rehearsal, so by the time of your spell the performance should go off without a hitch.
6) One thing I do additionally here is sigilize the final version of the spell. I take out the vowels and with one of each consonants in the text I construct a sigil as those who do chaos magick do. This concentrates the energy of the spell into a visual reference. The ritual should end up charging the sigil, which will also attract any residual energies of doubt, negativity etc. It can then be purified of these and burned on the altar as the final act of the ritual. Wipe your hands of the ritual (figuratively speaking) and you are done.