Build stop-motion models. The development of these will take time and expertise, but there are still independent production houses that do it. The process begins with metal work, building an armature that can be manipulated but set in a specific pose. The next step is to encase the armature in a clay mold that represents the monster. After the model is sculpted and painted, it will be animated frame-by-frame using a digital still camera to take the pictures.
Cast models in latex. To achieve a realistic flesh appearance, a soft material, such as latex foam, is used. This involves first making a clay model of the puppet, then taking a plaster mold of this. Finally, latex is poured into the plastic mold to cast the puppet itself. This can then be painted and manipulated to look organic and realistic.
Hide movable elements. While remote control armatures are available for manipulating monster puppets, it is often more practical to use a simpler device. The outer skin of the puppet, such as the neck of a snake, can hide a puppeteer's hand which performs an organic movement. Similarly, larger puppets can encase an entire puppeteer to animate the movement in real-time, similar to Guillermo del Toro's use of Doug Jones in the "Hellboy" movies.
Use KY Jelly for slime effects. The look of latex may appear like skin, but when it is dry, it does not appear organic. Often, special effects technicians will use lubricant to give their puppets and models a natural look. In John Carpenter's classic horror film "The Thing," Rob Bottin used copious amounts of KY Jelly to produce slime in his ground-breaking effects.
Take advantage of post-production effects. While major motion pictures have millions of dollars to spend on digital manipulation, there are some programs that are affordable and usable by amateur filmmakers. Post-production effect programs, like Adobe After Effects, can add extra enhancements to practical effects to make them more effective.