any tips to up bicep weights without a spotter ?
First of all, you would NEVER need a spotter on any isolation movements, especially curls.
Secondly, if you're the kind of person who uses a spotter on curls I don't even have to ask to know the spotter is helping you lift the weight. I don't know what happened but many people seem to think this is what spotters are for. They're not, unless maybe you're training negatives, in which case they can help you on the positive portion so that you can start a new rep. However, most guys think they're so macho if they can cheat curl (i.e. swing) big dumbbells and then have their "spotter" finish the rep for them half way.
Spotters are for safety purposes only. We recently had a debate on this issue:
http://www.ironmagazineforums.com/training/109666-no-spotter-help.html
As for the bigger biceps, curls are not the most effective way to build your arms. I know it seems odd, but the biceps are such a small muscle that training them directly elicits so few growth hormones. The biceps are actually designed to assist the much larger lats and other smaller muscles in pulling objects towards the body. Exercises like pullups and rows will hit your biceps very hard, as you're pulling much larger weights through greater ranges of motion -- all while simultaneously stimulating a great deal more of muscle fibres.
Better yet, if you train your legs with other compound movements (compound means you're using more than one joint...arm curls use one, your elbow...pullups use the elbow and shoulder) such as squats and deadlifts -- which are generally viewed as the top exercises in bodybuilding and even powerlifting -- you not only get the benefit of developing a balanced physique (as opposed to the "chicken legs" look that most young guys end up having) but due to the full-body nature of the lifts they produce more growth hormones than just about any other lift. The beauty of it is that growth hormones don't just sit in the area from which they were created.....they actually travel through your whole body. Believe it or not -- squats and deadlifts will make your arms way bigger than any curl or tricep extension could. Besides, with deadlifts and some squat variations your arms have to grip the bar and support major heavy loads! After a few sets of deadlifts my grip is usually torn apart. Imagine how much that must affect my biceps!
If I were you, I'd research push/pull full-body training. Read the stickies in the training section. There are some awesome articles. I gave up isolation last fall and my arms have grown about 3 inches since then. Hard to believe, eh? If you train your body according to its natural design -- that being the muscular system working as a system and not individual parts -- you'll see your physique go a long way. I guarantee it.