Who are you trying to summon? How long have you been working with that entity? Did said entity explain to you how to summon him or her? If you haven't followed the basics for a while, you're not going to succeed with your summoning spell. Or to clarify better - you'll succeed but you won't get who you want. Also some are more finicky than others and if you deviate from the traditional ways, they just aren't coming.
You said you're new so I would advise getting a few copies of different works to figure out which system of summoning you feel comfortable using. You can probably invoke early on - that just involves basically asking an entity to listen to you. A form of prayer. Summoning one before you takes a lot of practice and knowing what you're doing. Don't let this put you off though. It's worth it.